1. How much RAM do you have? If 4 or more, 64bit is worth going for.
2.W7 can be installed as either 32 0r 64 bit; dont forget W7 does not come with nor use Outlook Express - I use Outlook 2007, but Windows has an e mail service. Decide which e mail system you will use and Google to see how to migrate your e Mail to it.
Some use the "Update" but I used the "clean install" one. If the latter , do make a copy of all your data to an external HD
No real problem eith migrating IP Talk talk - do ensure you have all youe passwords etc, and the installation discs for other software.
1 User mans that MS only allow one PC at a time to use the OS you buy.