Dave is the best due to a ton of experence, but if your in a hurry good work sometimes takes time. Porting takes time and patience and the correct tools. I ported my heads myself and than had dave install bigger valves. He flowed tested them and there was minimual gains even though I thought I did an excellent job. The bigger valves gained me about 30% better flow after being installed by Dave. So I would not try porting the heads yourself. There are a lot of performance engines builders and pricing will be all over the place depending on the amount of work and skill levels. So there no way someone can tell you it will cost this or that for someone in your area. Just my 2 or 3 cents worth
Ken