ThinkPad accepts PPC2700 chips up to 2 GB.
Flip the laptop over so the underside is facing you, then, release the 2 clips holding the battery on.
Carefully grab the battery, then pull it straight out, not at an angle.
Unscrew the pictured screwed holding the memory cover in place.
Pry the cover open carefully (flathead screwdriver might help)
To remove the RAM memory stick, push both metal pieces holding it in place outwards, and the stick will pop up.
Pull the stick out carefully.
In order to replace the other stick, refer to the keyboard replacement tutorial. The other SODIMM is easily accessible with the keyboard removed.