Thema ie Problem with oil pressure.

[Odd Erik]

I have a problem with my Lancia Thema 2.0 ie gone 262000 km from 1986. The other day it stopped while out driving. After a few minutes I could drive it again, for 200 metres. and so on it further. The oil pressure lamp on the control panel lights when the car's stopped. When I got to have a good look at it I checked all hoses to the engine. Everything was ok. But when I started the engine (it would run maybe 30 seconds) It made sounds like it wasn't lubricated enough. My guesses are either the oil pump is broken or the oil filter is "jammed". The oil filter was changed along with the oil 4000 km ago. It uses a bit oil and I've filled 5-40W oil on it (cheap as hell) Does anyone know what my problem might be? If it's the oil pump is it a easy part to change? The car is in almost perfect condition and it hasn't given me or the former owner any problems. All servies done up to 1997.

thanks.
Odd Erik