Dave, glad you found Railpro before you became involved in DCC. I've done both and will not go back.
To answer your question, any locomotive that has a "DCC-Ready" plug is extremely easy to install Railpro in. All you do is plug the railpro module into the DCC-Ready plug and you are done.
Railpro can be installed in any locomotive, but some take more work. Larger locomotives are easier....an SD40-2 or a ES44 would be easy.
Look through the various threads on installs and you'll learn a lot. I made a video awhile ago going through a simple install in an Athearn ES44.,.. Should be easy to look up on YouTube.
Kevin