You could try running the upgrade advisor
though I'm not sure if specifically checks for 64bit compatibility. Did Lenovo ever offer 64bit (Vista or 7) for that model?
Actually, looking at Levovo's support page
it looks like there are 64bit Win7 drivers for pretty much everything -- even the Ricoh card reader -- so you should be good to go (Win7 should have base drivers included for most of the hardware anyway, since it's all pretty standard Intel mobile guts).
However, as Fox says, you're only going to see a net benefit from 64bit if you have (or anticipate installing) more than 3GiB of RAM. Windows x64 is a little cleaner architecturally, but the page tables required for 64bit actually take up a little more memory, so you only end up ahead if there was RAM sitting around going unused in 32bit. (And there may be a BIOS upgrade required also, if that model didn't support hoisting RAM by default). Or if there's a 64bit-only program you want to run (or code).