Cheapo valve spring compressor:
I already had a big C-clamp so maybe an actual valvespring tool would be cheaper than getting one, but a big C-clamp can be pretty useful around the shop for other things.
I bought a black iron pipe fitting, I think it is a 1/2" NPT coupler - both ends female threads, about 2 inches long. I hacksawed a big ass slot in one end. I tape it to the dead side of the C-clamp and put the live end on the valve face. The fitting goes on the spring retaining washer, compress it a bit with the clamp and you pick out (or put in) the retainer thingies out through the big ass slot.
As far as checking a head...
Check the cam bearing surfaces, once they are worn out, the head is worn out. There might be a way to resurrect one but I think another good head would be cheaper.
Check the threads on all the rocker cover bolt holes. These tend to get stripped easily; stripped ones can be repaired but I've found a lot of bad helicoils... you can use thinserts on most of the holes which is about 1000% better than using helicoils. If you have a pulled out helicoil hole you can repair it with a timesert or keensert but some holes are too close to another feature for that to be possible.
Check for warp with a quality straight edge or on a surface table. A piece of thick plate glass makes a fairly cheap surface table; not as accurate as a real ROA granite slab but OK for our needs. If it's warped you will need to have it machined flat at the least, if you have a good flat one it's a better choice.
Remove the valves and springs, mark the valves to go back in the same holes. Just drilling 8 holes in a bit of 2X4 and labelling them is a good system.
The insides of the valve guides should look smooth and bright. The valve stems should be tight enough that the valve drops gently in when the stem is coated with oil, not just falls in with a clank. You obviously do this with stem seals removed. Replace the stem seals with new ones if the guides are OK. If you need new guides, it is a machine shop job unless you have the press and tools to do it.
If the guides are OK then check the actual face sealing. I use a bit of fine valve grinding compound and give the valve a few light turns, then clean the face and seat and look at the polish pattern on both. If it's a nice circle about a mm wide on both face and seat, you are fine and shouldn't do any major refinishing, just a bit more polishing with fine compound. Burned channels or a wear circle that isn't an even thickness indicates more work is needed. Burned valves should be replaced, the stellite surface is very thin and reground valves may not last long (opinions vary). The seats can be refinished but only do so if they really need it, replacing the seats varies from impossible to very expensive and every time you refinish them the working surface goes further into the head affecting compression and valvetrain geometry.
Measure the valve spring free lengths and replace if they are close to the service limit. Unless you need them, don't use heavy duty springs - they cause much faster cam and lifter wear. The stock cam does not require special springs.
Porting is an art as much as a science. Matching the port openings to the holes on the carb spacers and to the header inner diameter is a good idea. Removing obvious casting flaws like odd lumps in the surface won't hurt. Reshaping the things should be left to experts IMO. Smoothing out the rough casting surface is apparently not a good idea.
