I've done a little bit of head work and to correctly "do" a set of heads, you're looking at some specialized tools. Most likely you'll spend more than you'll save over a lot of heads.
What you can do in your garage depends on what needs to be done. I've regularly disassembled the heads and had the machine shop grind the seats and valves along with installing new valve guides. Then I've assembled the heads myself, checking spring pressure and setting spring height. I also had the use of a valve spring tester at the time.
I've ground valves and valve seats using a friends Sioux valve grinder and there isn't anything you can substitute for that type of equipment. You can lap the valves with some grinding compound and a stick, but that really is OK if everything is in decent shape to begin with. If you have a GOOD straight edge, you can check for the flatness of the surface, but then you are still looking at a machine shop to cut the surface. Disassembly is easy as long as you have the valve spring compressor. Assembly isn't too hard, but you really should check pressure and assemble to the correct height. Then there's the valve guides. I've done those too and you need the various stuff to cut the existing guide and install the new guide and ream to size. Every big block Mopar I've ever taken apart needs exhaust guides at minimum.
To make a long story short, I can get the heads done at a price where it doesn't make sense to do much of anything on them myself. I don't even assemble them anymore... just let the shop do it.