Painless?

Having done 2 painless harness jobs what I learned was it color coded very well (mine were GM installs, mileage may vary lol) and the overall quality was pretty good. If I had to do another one the Fuse panel is probably not going to be under the Dash. IMO if you can get it to a different location the install will be cleaner and you have an opportunity to make for easier access.

And I can't stress this enough. Make a good wiring Diagram. Now that I am doing some Industrial electrical I can't begin to tell you how important a wiring Roadmap is.

But make sure your setup is worth a complete wiring makeover. To really make a nice job it takes quite a bit of work...

JW