how to strip the paint from a bike yourself?
John Allen has a page on refinishing a bicycle on Sheldon Brown's website. You need some covering on the frame to protect it, though. For aluminum, it is recommended to use chemicals and not sandpaper (due to particle embedding), but for steel, sandblasting is fine. The main issue with chemicals is fumes. 

There are also several related threads on bicycles.SE such as this one and this one.