Microsoft GP 9.0 Upgrade

We are about to upgrade to GP 10.0 from GP 9.0 (latest version).  We have the financial applications plus Business Portal, Integration Manager and Personal Data Keeper.

We have only one company that is about 80 gb plus the Dynamics database.  Our plan is to migrate the GP 9.0 system to a new (much more powerful) server first and then perform the upgrade there. We have no other third party addons or GP modules other than those listed above.

We plan to move to SQL Server 2008 on the new server.

My questions are:

We have received quotes that range from 2 weeks to 2 months. Based on the above, can someone provide a ballpark idea of what is a reasonable time (for a migration and upgrade)?

We have also considered migrating 9.0 and then doing the upgrade to 10.0 ourselves. We are quite experienced with GP 9.0 and did the original installation.  Based on the upgrade to 10.0, are there any pitfalls that we should be aware of?

As far as completing the migration, the upgrade and troubleshooting afterward, can you provide a worst case scenario in terms of weeks needed to complete the process (provided there are no significant mistakes during the process)?

Thanks and let me know if you need more information.