Okay, Ill bite-
Fact is, it all depends. Labor for a quality assembly by one of the local pros was 2 grand. That includes an entire blueprinting and analysis of the parts and their fit. Tuning is extra. This was from a pretty reputable shop. Without the reputation, you will likely need to start lower than that, and make adjustments to your prices (lower) if you cannot deliver the same quality that the pros do.
I think the best way to go about it is decide what services you can provide and decide what your opportunity cost is if you were to use that time to do something else, and base your prices on that.
I think in this industry, word of mouth advertising is very valuable. If your work is up to snuff, it should show in your own personal ride-that would be the best way to start...people will see your work on your ride and that can potentially develope opportunities. Hope that helps!