oil pressure sending unit

[alexei@wri.com]

Ok, folks,  I finally got to replacing the
oil  pressure sending unit that occasionally
messes up the oil warning light on my 87 Audi 4000S.

I've got terribly mystified by the attitude of 

local dealers and part people.
I've 4 different part numbers cited in 4 different
places with the price range going from $14.95 to $55.

Now, the are only TWO different oil  pressure sending units
in Audi 4000S and the one I am talking about is a smallish
brown thing quite close to the cylinder block.

Any ideas ?

Also, what precautions I am to take when changing the thing?

Could an average repair shop make much damage while changing it ?

Opinions appreciated.


Alexei--