Getting a bikeshop to put together a bike with a mongrelized set of components from different time periods is asking for problems. I would do the work myself for the most part, leaving only things such as sizing the bottom bracket and other such tricky things for the bike shop.
Bike parts tend to be easy to understand, the only problem is in the lack of standardization. I would be particularly wary of BB size and seatpost size. Both of those places, there are no real standards and fit is important. For instance, in the seatpost area, the diameters come in .1 mm increments.
If you are not mechanical, I would bring in just a few major components (i.e. frame, cranks, seat, etc) and buy all the smaller components such as BB, brakes, levers, handlebars, and so on from the bike shop. That way they can put something together that will fit, and if they scratch something trying to install it, it is on their hands.
In Seattle, we have a bike shop named Recycled Cycles which has a multitude of used and new components. If you can find a reputable used bike shop like that, then that would probably be your best bet. Make sure they have a good mechanic working there, not just some summer job teenager.
I have also done some business with Harris Cyclery
http://www.sheldonbrown.com/harris/ and have heard that the owner of the shop (Sheldon Brown) gives intelligent answers to bike mechanic type questions if you email him. He also stocks a lot of non-standard equipment; you can go there for your chainrings if you want. I managed to get a 49 tooth chainring which will fit on a Shimano crank from him.
BR