You should be fine with the heads, but don't set them on anything uneven while working and get them right back on when done. Leaning them in a corner of the garage will warp them.
Use the FSM torque sequence in reverse to remove the head and manifold bolts... the manifolds may crack if not torqued properly. Broken studs may have already done the manifolds in... give them a good inspection with a mirror before you start and try to have the hardware on hand so you don't delay reinstallation.
If you haven't removed many broken fasteners before... avoid breaking the extraction tools in the drilled holes... use a squirt can or bottle to soak them with atf several times over a few days before you get started. If you get lucky, you may be able to tap it out with a punch and hammer until you have enough to grab onto. I like to use a small drill bit to get a clean pilot dimple started, and once I have that centered and straight go to a bigger bit to drill through the stud... be patient, and careful not to drill into the head... cheap extractors are crap, and good ones are expensive. When what seems to be the "right way" fails, I have drilled the bolt/stud thin and jammed a cheap flat screw driver into it to wind it out, the cheap steel deforms enough to work, the good screw drivers and hardened extractors like to snap off and make life suck as you get to drill through tool steel.
If in trouble and unsure, snap a picture and someone here will have an idea... maybe a good one.
2 big thoughts to remember... don't grab the torches, heads will warp when off the block pretty easily... the old stud is the sacrificial piece, if you get one too buggered to remove with conventional methods you can drill it thin enough that you can get it to collapse and wind out... If you screw up the head too much... the party is over.
1 more neat trick, if you put a drill bit that fits snug into a clear hole, you can use it as a guide to keep your angle straight... very helpful if working on an angle.
