Being the ulitimate DIY''r, I always recommend doing it yourself. If you are not familiar with wiring techniques, get a copy of one of Nigel Calders books that covers marine electrical practices.
I have always been amazed at what people pass off as "Professional" grade marine wiring. My personal standards are pretty high, as I am an engineer, and spent a number of years working for defense electronics contractors and NASA suppliers, so I have a good idea of true "Mil Spec" wiring techniques.
Hiring sombody else is a waist of money, and would never be as good a job as a careful owner working on his pride and joy.
Older boats were strung with little more than household grade wires. The better ones used a product called THHN wire. But even though a "Mil Spec" wire, THHN was not tinned. Today''s best wiring is done using marine grade tinned wire. It costs more, is larger and may be a problem running wires in the same location as the skinny older wire, but it lasts much longer and is much better resisting corrosion.
When I re-wired Silmaril, I removed 25 years of previous wires. It was remarkable how many dead wires were lurking in the strangest of places!
Take your time to lay out how you want your panels to look, I prefer keeping AC and DC panels well separated and clearly marked.
Invest in quality hand tools, not the junk at the mass retailers. Look at a W.W. Graingers catalog or at Jensen Tool. Get top of the line crimpers, strippers, cutters, use quality lugs like T&B. Take your time. It''s really not that hard. The good tools and not trying to take short cuts makes all the difference in the world.