^no heat is required, and it could be something you do yourself if you have a mandrel and a deft touch. The only danger with using a crude instrument (some people say they can reshape a deformed tube with a big screwdriver) and too much force is that you can really screw up the seat tube below the lug...ask me how I know!

The other thing an experienced LBS may have is the proper tool for measuring, it's notoriously hard to get a good reading with calipers, and most people don't have either the sizer post that a bike shop might or a machinist's "T-gauge" (telescopic bore gauge).
http://www.amazon.com/Anytime-Tools-.../dp/B000I8NDAS
However, if you have a range of seatposts in the approximate size you think is required, the old "go/no-go" method always works.