Forget about the eclipse plugin. There is no advantage to use that, it's mainly just a way to use eclipse as your text editor (no full functions). Linux support is possible, but only with third party compilers for S12. If you are a CodeWarrior user, this will not be an easy transition. Debugging, code compatibility, and behavior will be not be the same.
My advice, for simplicity, is to just install CW 5.2 Classic and follow these steps to add support for the MCS12DP512.
How-to Add missing derivatives to CodeWarrior Classic HCS12(X) 5.2 (Unofficial Method)
By the way, what type of programmer/BDM do you use?