1 as far as I know WindowsUpdate is a program on its own and will be able to check for updates even if you have no browser .as microsoft and eu have not yet sorted all the details ,maybe you will have a choice of browsers through windows update . just a thought.
2. I dont know for any lists ,but I have tested extensively all the later versions of windows7 in 32 and 64bit .in 32 bit everything works as it did in vista including all my hardware drivers .64 bit wont accept unsigned drivers and has refused several drivers of mine ,I cannot get either of my wireless internet adapters to work .
3. install the 64bit version ,dont use the product key you will have 30 days to test ,if you dont want to keep it simply remove ,microsoft will be none the wiser ,if you install either without using the product key you will be able to do this .once the key is registered ,the key you use will be locked to that system (32 or64) and you wont be able to change. although the wording of the EULA suggests differently ,I believe that to be the case .
4. it should run superbly on your specs. it is noticably faster than vista , and uses memory and multicore processors better .