My First 318 Rebuild

Alright, after a longer hiatus than expected, I'm back to actually building this engine. I was chatting with my coworker and he was saying that I should get the heads gone through by a machine shop. I've gotten them disassembled except for 2 exhaust valves on each head. These all won't go through the guides without significant force, so I haven't removed them.
The heads are off my 69 318 block, and never had any problem other than stem seals, they cc out to 60, which gets me close to my compression goal.
What steps are necessary for basic refresh of heads, as well as what would be "best to do" but not required? Links to threads I haven't found are great, no need to rehash stuff that I can read somewhere else.
Trying to stay budget conscious so anything I can do on my own I would like to do