Start by swapping the L.R. inputs on the amp.If it changes sides, it's in the patch cords or head unit. If not, it's in the amp, speaker wires or a speaker.
Brakes $200, fork tubes $500, electric $20-$500, tires $200+, original headlight bucket $??? and a whole lot of labor and who knows what other little parts and such.
I had one in the early 90's. Loved that bike. One of the bikes I wish I wish I hadn't sold.
I'd like another someday, but the only way I'd get this one is if it was free and brought to me.
These may work for you. Adjustable shackles.
https://www.prgproducts.com/product-page/frontier-xterra-rear-lift-shackles
PRG also has a lot of other options.
Had cat named Rocky, his nickname was Crack Rock. Every now in then he would escape. Neighbors look art you kinda funny and then go back inside when you're hollering "Crack Rock" outside in the middle of the night.