318 head porting for the average joe

Thanks to all you teachers, and sharers of great and valuable knowledge, this has become my fav thread. Hats off to those who know and don't mind sharing. you guys are rare, and classy.
Now for some questions. Being new to this type of hop ups, and clean ups, modifications, how far can we newbies go and not get into water or oil jackets and ruin a good head? that worries me most is not knowing how far we can go for certain, and how to know how far not to go. ALSO.. whats the chances of maybe doing an at home three angle valve job, for us guys who really like saying, well ya see, I did it all at home in my shop( garage)?