Do you already have the right tools - flexshaft grinder, die grinder, bits, etc.? At a certain point you have to determine if buying the tools or paying someone to do $300-500 of modest bowl and port work is the right way to go. If this is your first set of heads you'll be porting, I also wouldn't recommend using carbide cutters. Use sanding rolls and WD40 instead. It's a lot slower but harder for you to really screw something up quickly.
That being said, a turbo motor is still an air pump, and anything (like porting) that help it pump more efficiently will pay off in power.
I also have not seen any good books on LSx porting, but I have had great luck porting my own SBC heads to David Vizard's books.
Jim