I've got a '91 Stanza that has served me very well for about 8-9 years. It has 94K miles on it and I drive it to work every day. It's just started to leak coolant from the intake manifold. I figure this will be an expensive repair.
You need to isolate the source of the leak. Could be simply a hose leaking. Pressure test the coolant system and find the leak is all I can advise. Until we know what the problem is, we can't estimate the cost of repair.
Well... I was right about the intake manifold. Brass fitting leaking and it's part of the manifold. Coolant is rusty (I guess that would be my fault!). So, I'm probably going to donate the car to charity or something.
I gave it to the son of a co-worker who was looking for something "cheap to drive." He pulled the intake manifold and replaced one of the tubes. Put the manifold back on and discovered the other tube was leaking too. (Doh!) Called a junkyard and had it hauled off. My deal with him was that he could have it for free, but I wouldn't take it back. Hell, it had a half a tank of gas and the tires were near new!
His dad also said the main bearing was squirting oil. Personally, I find that hard to believe -- I may have neglected the coolant, but I really babied that thing otherwise and it never leaked any oil. Mobil 1 every 3K miles, etc.
Anyway, I got a used '07 Altima 2.5S and other than having car payments again, I love it.