1992 Toyota Previa stereo/wiring probs

Just tried installing a new stereo in my van. Trouble is i can not get the yellow wire connected to the live wire because apparently there must be a short somewhere......it does work when I connect the stereos RED / yellow to the ignition, but it loses memory whenever I turn off and on. I dont know what I did afterwards but suddenly now my clock in the van reset to 1 oclock and the lights got dimmer. If I try to turn on the dash lamp the clock goes out and the dash light does not come on and when I turn the dash light off, the clock comes back but resets back to 1:00. When I turn the ignition off and come back 10 minutes later, the clock picks up the time from when I turned it off........I a, no car guru, but did I seriously screw something up and I definitely wont be able to fix myself..............What kind of money would I be looking at to get something like this fixed.......I really appreciate any anyone can give

Thanks but that didnt work...........It wont evem come on now if I hook the yellow and ignition up to the switch, so I must have fried something.....Since I dont know what I'm doing, I'm just gonna take it to the dealer and hopefully it wont be too much to fix the wiring. Thanks for all your help

I would say to check your fuses, maybe that's what's messing up your van's constant wire.

Thanks for all the suggestions, but I took the van in...........the whole harness for the stereo could be screwed up..............Just out of curiosity which fyse would control the constant wire........the radio fuse, I really am stupid when it comes to auto do it yourself