We have not yet decided on the desktop/laptops for our exam rooms in our two physician internal medicine group.
1) You'll want to hold off until you establish the number of workstations as Jon (JBS) pointed out. If you're planning to use thin clients, then that server you listed above will not suffice. It would also help to have an idea of the number of workstations/users.
2) 64 bit all the way. No reason to use 32 bit anymore. If you use 32 bit, then you can only use 4GB of RAM.
3) Not sure.
Also, you might want to get Small Business Server 2011 instead. You get a lot more features for the money. Onsite email solutions (Exchange), SharePoint. You can find the server recommendation thread here:
http://amazingcharts.com/ub/ubbthreads.php/topics/40565/Server_Hardware_Recommendation#Post40565