It's not so difficult, when you have the proper tools.

First - be sure your oil filter is OK.

For VW BEF engine, the oil pressure switch is in the oil filter bracket, on the top of the engine oil filter. It looks like the nut with long grey electric pin. It is a VW part (Part No VW038919081M)
It may be checked, but you need a tester for it.
The switch should'nt cost more than 10 USD.
The engine oil pump No is VW06A115105B.
Shouldn't cost more than 100-130 USD.
If you have no experience, bring the technician, who has some skills with engines.
Believe me, you will not spent a fortune ;-)