oil sending unit? & lean exhaust code?

hi there!
'93 s10 2.8L v6
i was told to replace my oil sending unit and i don't have a clue where it is. can anyone steer me in the right direction?
also, i have a "lean exhaust" error code stored. can anyone tell me what might cause this?

rust holes in my muffler??????????

thank you everybody!

With my 85 2.8L 4x4 the sending unit is right beside the oil filter, and pretty easy to change.