2001 Sunfire Gt 2.4l Engine Diagnosis Help

hi
i have been looking for a sunfire for my daughter,i have found the following one owner sunfire gt with some possibly serious engine proplems.
fully loaded sunfire gt with 2.4l 5 speed drive train.
owners wife brought car home complaining of ticking noise in engine.
oil was at proper level and car showed no signs of over heating.

here is the email i received from the owner:
it never overheated, but there is compression blowing up when you take off the oil cap. it is a 2.4 and my wife came home one day and said that the car had a ticking noise in it. i went out and checked it out and it has a tick on the rev. i checked the oil but it was fine but like i said there was some compression blowing up when i took off the oil cap. the car still starts and runs fine. i haven't driven the car since afraid of doing more damage. i was talking to a mechanic at marriots garage and he said that it could be a head gasket or the timing chain. it could be a valve, i don't know but if you are interested give me a call and drop by. the price is a little negotiable. but it never overheated .

another email from owner:
no oil in the antifreeze or antifreeze in the oil that i could see. a couple of little surface rust spots but nothing serious. the car is fully with a monsoon stereo system which was extra when i bought it new. 16" rims and 55 series tires, power sunroof, cruise,power mirrors and windows and the ac works perfectly or it did last summer. it has factory smoke tint on the dr and pass door windows and trimline tinted out the small back and the rear window with the darkest legal tint when i bought it. the car has mostly hwy kms on it and i changed the oil regular every 8-10,000 km.

so the symptoms are:
no oil in antifreeze and no antifreeze in oil.
engine starts but ticks quite loud.no other noises.
i am wondering what the possibilities could be,car has 160000kms on it.
he is asking $2200 can obo,i would not mind putting up to $300 into the engine for repairs.

so i guess the question is what problems would give the above symptoms,i am familiar with the 2.2l as we already have a 2005 cavalier and 2005 ion.
i am not familiar with the 2.4l engine

head?
valves?
complete head?
head gasket?
spun bearing?
timing chain
tensioner,etc.
what could cause compression from the oil cap(plugged pvc valve)?
what are common major problems with the 2.4l

thanks,jeff
i can be emailed directly at kbg1@eastlink.ca