You will likely be able to run it fine, but what spec do you have? To be honest the main reason you would install a 64bit version of windows is to utilize 4gb or more of Ram, as 32bit systems will only use upto 3gb. So if you have more than 3gb then go for it and yes your system at that spec shouldnt have any problems, infact it may even be slightly more stable.
However, you will have to do a clean install, you cant upgrade from 32bit to 64bit without formatting. Also you are likely to find that some of your pc periphirals and software packages you currently use will no longer work on 64bit, so research it first, you may be lucky
But again you shouldnt worry about speed if your wanting to go to 64bit becuase the main reason for going to 64bit is to better utilize a higher spec pc, if you dont have a high spec pc dont bother with 64bit, simple.
Hope that helps.
Dan