onan not cranking

onan Emeral Plus 4000, in my 1998 class C won't crank. It was starting and running until a few weeks ago and I was trying to start it and it was cranking, but would die I believe maybe I tried this too often and maybe something happen to the starter. fuel is full, batteries fully charge. I can hear the solenoid trying put starter not engaging. I can't get to the starter it seems without removing the onan. it is on rails with 4 bolts holding it in. Can anyone tell me how difficult it is to remove the onan from the coach and if you did, how to go about it. If I can get to the starter I probably can repair it myself. There is a shop where I live that can repair the starter for $35.00. Any help or suggestions please? And I gorgot to mention I have already cleaned positive and negative cables. Thanks