Upgrading a T41 Question

[arun]

Hey. I have a T41 2373-DHU that needs to be upgraded.
I thought of 4 possible things that can be upgraded

CPU - Which one will fit and what is the fastest one I can get, Cost?
RAM - Already added 512mb, total now 768mb
Wireless Card - Need to get G, since the one installed is B , which one?
Hard Drive - Which one? Speed? Cost?

So I would like to know what are some of my options, how difficult is this process and what would be the cost.

Thank You,
Arun