two weeks max if you know what your doing!
how do i know? im doing it atm!
It involves moving the content DB, this is what i have drawn out:
1) Run prescan.exe 2003, check there are no errors before proceeding
2) Go to SharePoint 2003 SQL database, backup content DB
3) Go to SharePoint 2007 and create a new Web application
4) Detach the SharePoint 2007 web application from the new content DB
5) Restore from the backup (2003) to the 2007 DB
6) Go to central admin and attach 2003 content DB to the SharePoint 2007 web application.
8) Make sure all is running correctly on the farm
9) Review upgrade log file
10) Run prescan.exe 2007, make sure there are no errors
11) Do same again for 2010 following the same steps above
12) Run prescan.exe 2010
13) Review the report generated by the custom utility
14) Configure access security
15) Rebuild search index
its a complex issue and will give you a headake! im presuming that you will do a dummy run first ;), you need to also make the layout in SQL and sharepoint 2010.
the content DB is called a complex double database upgrade approach :) , but if its a contractor I would have it at 2 weeks!! 3 to be on the safe side!
Also bare in mind that it will double your SQL database due to the fact that 2003 - 2010 DB is vastly different and in any upgrade the DB would need other tables procedures ect to make the link, compared to a fresh install of 2010 and a new DB! As you can see im upgrading with an intermediat (wss 3.0 sharepoint 2007) as there is no direct upgrade and server 2003 needs wss 2.0 on sharepoint 2003!