I am assuming MOSS2007 base install is English/US and just the single MOSS language pack for French has been added.
Useful resources and pieces you will need
Base WSS SP1 - 32bit and 64bit - http://www.microsoft.com/downloads/details.aspx?FamilyId=4191A531-A2E9-45E4-B71E-5B0B17108BD2&displaylang=en
Base Moss SP1 - 32bit and 64bit - http://www.microsoft.com/downloads/details.aspx?FamilyID=ad59175c-ad6a-4027-8c2f-db25322f791b&DisplayLang=en
How to Install WSS Software Updates - http://technet2.microsoft.com/windowsserver/WSS/en/library/91649a7e-6b5a-4e5a-9ee5-51951f4b857f1033.mspx?mfr=true
How to Install WSS Software Updates - http://technet2.microsoft.com/Office/en-us/library/f484f5f2-35bb-4d70-bf56-dd1c4c287c721033.mspx?mfr=true
How to Deploy ALL MOSS Server Updates General Information - http://support.microsoft.com/kb/945013
Language Pack Download for WSS SP1 - http://www.microsoft.com/downloads/details.aspx?FamilyID=05046b1d-dd7b-456a-8838-8d978c5f3579&DisplayLang=en
Language Pack Download for MOSS SP1 - http://www.microsoft.com/downloads/details.aspx?FamilyID=3a6c26fd-0beb-40d5-8cba-15164faab150&DisplayLang=en
There is a generic sequence you can folllow for each of the updates. You have 4 service packs in total that need to be deployed to a total of 6 servers.
The running order is server hosting the central admin site followed by all the others.
The SP installation order is WSS SP1 > WSS Language Pack SP1 > MOSS SP1 > MOSS Language Pack SP1.
Although the suggestion below indicates you need to run the PSCONFIG utility after each service pack install strictly speaking that isnt true. In the case of a WSS SP1 and MOSS SP1 install you can install the WSS SP1 binaries immediately followed by the MOSS SP1 binaries. After both of these have been completed PSCONFIG can be used to upgrade the farm for both service packs. The reason I suggest running PSConfig for each SP is that in the event of an upgrade failure it will make troubleshooting that much easier.
For each Service Pack do the following
1. Disconnect users from the server farm by stopping the World Wide Web Publishing service (w3svc) on all Web servers.
2. Begin the software installation on the server hosting the central admin web site
3. At the end of the software update installation, the SharePoint Products and Technologies Configuration Wizard start
Note: If the wizard does not start automatically, click Start, point to All Programs, point to Administrative Tools, and then click SharePoint Products and Technologies Configuration Wizard.
4. On the SharePoint Products and Technologies Configuration Wizard Welcome page, click Next.
5. In the dialog box that notifies you that some services might need to be restarted during configuration, click Yes.
6. On the Completing the SharePoint Products and Technologies Configuration Wizard page, click Next.
7. When the dialog box about installation in a server farm appears, do not click OK. Instead, leave each server with the following dialog box displayed: - THIS IS CRITICAL TO THE SUCCESSFUL INSTALL
You must run Setup to install new binary files for every server in your server farm. If you have multiple servers in your server farm, run Setup and the configuration wizard on the other servers now, and then return to this server and click OK to continue.
8. When the dialog box from the previous step is displayed on all Web servers in the server farm, use one Web server that hosts the Central Administration Web site to finalize the installation.
9. On the server you selected in the previous step (Step 2), click OK.
10. On the Configuration Successful page, click Finish.
11. Continue updating the remaining computers in the server farm, one at a time, by clicking OK in the dialog box.
Note: It is important that the SharePoint Products and Technologies Configuration Wizard perform the configuration procedures on only one computer at a time.
Again, once the first farm member has completed the upgrade you can complete the upgrade on all the other machines in parallel since all the database upgrade steps have already been completed.
When the software update installation and configuration is complete on all the Web servers in the server farm, make the Web servers available to users by manually starting the World Wide Web Publishing service on each server on which you manually stopped the service.
OK after this you can move onto the next service pack in the list.
You can verify successful install of the servicepack by following this process after Step 10 above.
After you install a software update, you should verify that the installation was successful by reviewing the upgrade log file (Upgrade.log), as described in the following procedure.
To view the upgrade log file
1. Use Windows Explorer to navigate to the %COMMONPROGRAMFILES%\Microsoft Shared\web server extensions\12\LOGS folder.
2. Use a text editor to open the Upgrade.log file.
3. Scroll to the date on which you installed the software update.
4. Search, or visually scan, for the following entries:
Finished upgrading SPFarm Name=<Name of Configuration Database>
In-place upgrade session finishes. Root object = SPFarm=<Name of Configuration Database>, recursive = True. 0 errors and 0 warnings encountered.
If you find these entries, the installation was successful.
5. If you do not find the entries from the previous step, you can identify specific issues that may have contributed to the failure by searching, or visually scanning, through the Upgrade.log file for the following terms:
After you identify and resolve the blocking issues, you must force a software update
To force a software update
1. Force a software update operation by opening a Command Prompt window and changing to the following directory:
%COMMONPROGRAMFILES%\Microsoft shared\web server extensions\12\bin\
2. Type the following command:
psconfig –cmd upgrade –inplace b2b –wait –force