You can have a look here -->http://www.linux-on-laptops.com/
and see if someone else has installed a distro on that model. My experience with Thinkpads is good with linux.
If you are going to try one of the buntus, 10.04 is out. Go with the latest release. Mandriva is a good choice also. I like its intaller and the tools for configuring better than Ubnutu. I run them both, I have 10.04 on my HP Mini netbook, and Mandriva on my desktop system.
The specs you listed shouldn't be any problem at all. Wireless cards can be a challenge. You didn't say which one you have.