Just uninstall the old one and put the new one in and pray. Seriously though i dont think it will be as big a jump as last years was from 08,it should work........i hope :S
If your computer can handle FM 2009 then it should handle FM 2010. I think they have been working on optimizing it a bit so that it should be a bit smoother than FM 2009 was.
as the guys have been saying if fm09 works then fm 10 works and i wouldn't really recommend keeping both on the same computer so unistall fm 09 and then install fm 10 when it arrives
kris showed me a screenshot on fm10, after you select what leagues you want, it tells you your computer performance, and how fast it will run the game, check the "your all raging" thread.