Well, I'm not VMF... but I can try to answer a few of your questions :). Well, if your feeling vibrations in your steering wheel, it may be wheel balance up front... if your feeling it in the seat, then it may be in the rear. I would check to see if it's balance because it is cheaper than alignment. Well... a nicely maintained 91 LS 400 can go for a while, Im driving a 92 LS 400 with 198,000 miles and it is fine, everything is well, and I think i can get prolly 200,000 more miles lol. All i really need to do now, is to replace the front and back brake pads, and the car needs no tune-ups :) With all the problems you've listed... i doubt you could sell it....