if i change to the developer version, will i have to reinstall the hijack kernel?

Yes.

Installing new software on the player overwrites the kernel. However it is very easy to reinstall the hijack kernel and it doesn't hurt anything to do so.

What are the major differences between the two versions.

The shell prompt is available in the developer version. That's the only major difference.

Both of these questions, and many others I'm sure you'll have, are answered in the FAQ here and here.