Building a simple bookcase is pretty easy these days, you can buy the plywood and wood already cut to measure and assembling one with one of the following plans should be easy for anybody with common sense and basic skills.

http://www.bunnings.com.au/site/files/5709/How%20to%20make%20a%20timber%20bookcase.pdf

http://www.taunton.com/finewoodworking/pages/w00018.asp

http://www.plansnow.com/dn1120.html

bringing in a carpenter whould probably have an overhead if it is only a small project, for a large library project it is certainly worthwhile.

anyhow the advantage of doing it yourself is that you get to keep the tools , and the rule of thumb for many woodworking project is that what you save by doing it yourself ( calculating materials, tool costs and labor - your time) is usually equal to the value of the tools. but then again you get to keep the tools.

enjoy