1994 Toyota Camry Gear switch adjustment

I think I need to adjust the park/neutral switch, but can't seem to get the plastic housing up so that I can get into the bolt in order to loosen the bolt and readjust the position of the switch/lever. What is happening is that the car won't turn over at times unless the shift is pulled backward just a little. Secondly, on trying to use a lower gear as a break to control speed when going down hill, unless a little backward pressure is continuously on the shift lever, it slips out of second and leaves the car in high gear. At the same time, the "2" indicator on the dash goes off unless a little backward pull on the shift is continuously done. The back-up lights, also, don't light up unless backward pressure is held on the shift lever. Toyota wanted $375 to put in a new switch. (I don't think they ever heard of adjustment!)

I need to know how to get in to make the adjustment or any other advice you may have. (I thought it was the starter motor that was at fault--replaced that, but the problem continued.)

Thanks!
Cyril