Any Info Will Be Helpfull

So I went and picked me up a kia sportage FE3 engine today 260 miles round trip, but it was FREE . My question is does anyone know how hard it is to rebuild one of these engines, mine has low compression so i want to go through it while its out of the truck, im thinking that its the valves makin it have low compression, if anyone has a thought on what might cause this let me know thanks to all in advance
WILL

could be rings, maybe the head gaskets blown?

i would check the head gasket. that would probably be the easiest to fix.

yea i was thinkin that too thats why i wanted to go through the whole thing before i put it in my truck. I also plan on buying a gasket kit and replacing all the gaskets i can just to be on the safe side to include the head gasket, front and rear main seals, pan gasket....well you get the point lol thanks guys