Working on the engine out of the car is much easier mainly because of the timing chain housing, trying to work on the engine and set the timing with the engine in the car leaves a very little amount of room to work with between the chain housing and the body.
The engine can come out the top or even be dropped out the bottom(GM put them in from the bottom fyi). If pulling the engine out the top separate the trans from the engine, remove the intake and exh. manifolds and as much other stuff as you can from the engine then lift it right out. Some people lower the trans and engine together(or separate)and then lift the front end of the car high enough to slide the engine out, many people say going out the bottom is easiest, its all preferance and what is most comfortable for you really, worst part about going out the top is you can bang up the engine bay if not careful when raising the engine, dont try to lift the engine and trans out the top together, it can be done, but its a real pain due to the brake master cyl. and the angle that the engine and trans come out at is pretty extreme which makes it hard to handle and leads to damaging the engine bay.
On the other hand you could leave the engine and trans in the car and pull the head off, usually people just let the chain housing dangle there loose because they cant get it out from between the engine and the body, many people do it this way because they have no hoist and have the common head gasket problem, its just viewed as being harder due to the limited amout of room to work, kinda a trade off in work I suppose- either pull/drop the engine for and easier job, or leave the engine in(less work)and deal with the limited hand and tool space etc. Since you dont have any bottom end work needed it may be easiest to just pull the head off while the engine is still in the car, again its really personal preferance.
Be sure you have a manual and research as much as possible, for instance there are new head tighening sequences and specs released since some of the manuals were made, on the net you can find the best way to rebuild the motor, again check out
http://www.quad4forums.com/forums/ a ton of info can be found there, the active members of the board are experts on the quad 4 and are usually glad to help, alot of topics already covered in there so try the search button first if you like.
Which version of the quad do you have?