I've been debating the same question, but fro a different reason. I need to replace my shift cable and figure if I'm going to do that, I might as well get the rest of the back-end (bellows, gimbal bearing, u-joints, etc).... i think the key, as previously mentioned, is having the right tools. In addition to the puller and seater mentioned above (both fairly cheap ar Harbour Freight ~%50), you will also need an alignment tool which it appears the best deal is on eBay ($100-150) - someone coulds start a nice business doing online rental of these tools
There are a ton of articles out there, even some YouTube videos... I'll try to document my adventue and post back... hope to get it done in the next couple weeks.