1995 Chevy truck doesnt want to reverse
 

Bought truck a couple of weeks ago. It's a 1995 Silverado with 4wd. Put a lot of money into it already. Truck sat in AZ heat for 1.5yrs. Truck is running good with all the work but now it doesn't want to reverse. All other gears fine, shifts fine, but when in "R" it's just like Im in "N". A couple days ago it was shimming in "R" now this.. Please help ASAP.. Also, "R" and "D" don't light up on dash.. Thanks.