Cranky Engine...

I've got an 88 Laredo that's got 173k miles on it. It usually starts, after multiple cranks and rattles like crazy (something to do with the oil possibly? Not a mechanic). When I had it in the shop last fixing the rear main seal,t hey said that 4 of the 6 cylinders were running on ok compression rates, but the other two weren't. The motor is weak, has no "go" and is very unreliable. Any solutions to this problem besides the obvious rebuild/replace, because my budget currently won't allow that.

Also, I've got oil leaking out of the top of the head where you add the oil. The cap just turns to lock and the oil comes out form there. Suggestions?

I appreciate all help in advance.

Anyone had any advice at all?