1990 Mazda Miata Buying 1990, when selling 2005

1990 Mazda Miata 175000 miles

Hi, I have notice from my mechanic I have 1 year left on my nissan sentra 2005. I want to replace with a 1)used car, 2)convertible. Near me is a 1990 MX5 Miata for $3850. Knowing the Miata is a big step up from my Sentra in price. I don't know how many years could be left on the Miata. Could I spend a little now and begin to save again? I don't think I can afford to take advantage of all 'new' car deals with a car payment. I have a mortgage pmt, condo pmt, each month plus utilities and I'm on social security disability, maybe I should stop dreaming.

Thanks so much for your kind help!