Since FMP 7 and FMP 10 files use the same file format. There's no real conversion that takes place here. You just get the additional new features that have been added since FMP 7 was released. I'd make that change first.
The major change will be Snow Leopard. Judging from the numerous posts here, I'd read check out those posts first to see if any might raise an issue for your database and read up on them before making that change.
I am using fm9 and recently upgraded to snow leopard from 10.5.6. No transition issues regarding fm9. Have other issues with snow leopard, however thats for another forum.