Saturn Repair: fix it or trade it?, saturn wagon, slow traffic


Question
I have a 97 Saturn wagon that won't start (everything works, just won't turn all the way over).  Dealer says it needs a new computer (it was acting possessed: locks and wipers turning themselves off and on, various warning lights doing the same etc.)  Was also overheating when in extremely slow traffic (steam from radiator, tho full of fluid).  In addition it needs an allignment and brakes. bleah.
Nothing has ever been wrong with it before and I have keept all the fluids changed regularly.  
Problem: it's not paid off yet, and trade in value is alot of nothing in current condition.
Other Problem: if I fix it, how much longer can I expect it to last? It has 180,000 miles on it and I drive a minimum of 100 miles a DAY.
Final Problem: I know next to nothing about cars and really need some advice.  I would appreciate any possible help or advice- this is my second saturn (first one was stolen!) and I have found them to be great cars overall-  Thanks for your help!

Answer
HI well icant say what u should do i think if u take it in the dealer and get them to give u a quote on how much everything will be and then figure it out... also on how much longer it will last i have seen some of them go to 300,000 so i would be lying if i gave u  a number u should take it to the dealer and get them to give a good going over thats the best i can do sorry and good luck