I take it you are talking about a PV course that will lead to the students taking the NABCEP entry level test. I'm not aware of any train the trainer classes that are taught on a regular schedule. They tend to pop up here and there but it is hard to plan for one. It might be a better plan to just take the entry level PV course from someone else and see what is covered. For the most part the entry level course is really basic.
I would recommend the Photovoltaic Systems book as a good starting point. It is used in many basic and advance PV classes. NABCEP also has the task analysis on their website that lists what a person should know at each of the different levels for their tests.
Expect to be teaching people who have absolutely no background in construction, electricity, or really anything useful to the class. In the entry level classes you are starting fresh. I have taught the advanced PV class at a local college and several of my students have gone on to teach the entry level class other places. I got the students who passed the entry level class and I still had to go back over some basic concepts.
Since you had an instructor for the course before make sure you get their class syllabus, presentation materials, quizzes and tests, etc for the class before they get to far way. Making that up from scratch is a lot of work. When I made up the advanced PV class I think I made the equivalent of $0.25/hr that semester with all the outside time I had to put in.
Good luck and have fun.
