Hi mate
I have recently converted the rtr from rear motor to mid motor 4 gear. The below link takes you to the main durango site but scroll down and it shows what parts to buy
http://www.team-durango.com/race-cars/dex210rtr/
You do not get the instruction manual with the rtr either so is worth searching for the durango 210 instruction manual and use this to convert
Hope this helps