hifi engine

yamaha k-1020

HI, I need help. I bought used a k -1020 yamaha casette deck. plugged in it was making funny noise put tape in nothing? so opened up and could see from inside behind where tape loads into deck that there was a little round tire with rubber belt material on it then i noticed some bigger alumnium wheels 2 with broken belt on them i ordered a belt kit and idler tire. how do i take apart and install this stuff no manual any help would be apprieated thank you