Whether or not it is a good thing to do is completely up to you.

A good way to do it will depend on the kind of rear dropouts on your bike. If they are vertical -- the wheel drops down out of the bike -- they you will most likely need a tensioner of some kind to pick up any chain slack. There are a number of different kinds around and if you are exceptionally cheap, you could even use the existing derailleur as a tensioner. If you have a horizontal or near horizontal dropout -- single speed/fixed gear or older geared bike style -- you don't even need a tensioner.

Cabling back to the IGH hub can be tricky as well, depending on how the cable is routed and what hard frame stops came stock on the bike. But not insurmountable.