Starting the upstairs plumbing remodel

It is time to start on the upstairs bath remodeling. The first step will be the rough in plumbing.

All the fixtures have been removed, along with the entire flooring and subflooring. I would have liked to salvaged some of the old Fir hardwood flooring but it was in such a decayed state, that it wasn't worth the trouble. The previous owners, when they put down tile, failed to put down an adequate underlayment, that water soon leaked through to the old floor and damaged them.

I put together a rough drawing (below) on existing and future modifications, to help aid the plumbers on what would be required of them. But after receiving three quotes in the $4000 range, I desided to pick up a $20 plumbing book, a collection of plumber tools and emailed a friend in Minnesota who's a plumber. Are all plumbers this expensive, and for only 6 hours of work?

I figure I'll do most of the work myself, and if I get into trouble, I'll hire a plumber by the hour. The only tricky part will be the center drain, which won't have traditional venting...