Does the fuel sending unit need to be replaced, or can just the level sensor be replaced, they are 2 seperate parts:banghead:

Are you referring to thw whole fuel pump assembly?

The fuel sending unit and level sensor are one and the same. The fuel level sending unit can be replaced separately from having to replace the whole fuel pump assembly. See pic below.

http://i5.photobucket.com/albums/y186/lizzywiz/fuelsender.jpg

If I remember properly, your car is an 01 SE 3100 (will also fit SE and GT w/3800, GTP is different). You can buy the level sensor separately from the fuel pump module.

level sensor = AC-Delco part# SK1051 (GM# 89060197) dealer retail $160
module assy = AC-Delco part# MU177 (GM#25331861) dealer retail $460