Suzuki: reviving my zuk, electronic fuel injectors, head gasket leak

Question
i have a 1993 16 valve 1590cc/1.6l 4x4 Suzuki sidekick EFI that is partially alive. Many problems with it and i am struggling. Well, it cranks over with difficulty and when it does turn over the engine quickly dies. I found a lot of oil leaking into the spark plugs. I am dreading intake manifold or head gasket removal. How do i diagnose a head gasket leak and intake manifold leak?. Other problems include a lot of rust that has frozen the fuel filter bolts and nuts tight, i have tried every rust penetrators available, any ideas?. I believe i am not getting fuel so i thought to change the filter and possibly the pump. I am at the disassembly stage and i am keen to start cleaning however i do not want to do unnecessary work. so in a nutshell, i have a lot of work a head of me, lots of time but limited finances. in summary i have cleaned the air cleaner and filter, drained the radiator, coolant is fine, the electronic fuel injectors need cleaning, the distributor cap and rotor are good and carbon free. the hard bits i am dreading are the head gasket and intake manifold. i need help in diagnosing if they have issues before i tear them down. sorry for such  long winded problems. any help is much appreciated.
many thanks
damon

Answer
The intake manifold does not have oil pressure to it,so it's probably not the issue.  You need a leak tester, and a source of compressed air.  Perform a leak down test, and see if there's air coming out of the valve cover - that might indicate a ring issue.  You need access to a service manual, and procedures for doing testing.  Try the library, or the internet, I can't describe everything about the tests because which test to do would require that I be able to get a
feel" for the situation, in other words be there.  The next best thing is for you to "go to school".