Siding choice does make a difference in resale value. See Remodeling Magazine's Cost vs. Value report for details about your area.www.costvsvalue.com
Pricing really does vary from area to area and is largely dependent upon who you choose. My advice it to make sure you are working with a solid, respectable company who has been doing this a long time. The species of wood and the finish you are looking for may require different techniques - and a pro will know what those techniques are.As for moving items, I always consult my clients to remove items from all rooms and have all connecting areas refinished at the same time. While there are methods for "blending" one are into another, I have yet to see results that I consider acceptable. Doing it all at once is the right way.