By no reverse do you mean "NO REVERSE" or "SOMETIMES IT WORKS SOMETIMES IT DOESN'T." I have the latter of the two problems. It goes in about 80 percent of the time (usually when I could care less if it does). But when I really need it it never engages. I took it in to a tranny shop to see how much to rebuild it and they said about $2500. So, 45,000 miles later I still deal with the problem. I have gotten used to not getting myself into situations where I have a life or death need for reverse, so it's a problem you don't have to fix right away. If you off-road a lot you'll probably want to get it fixed. Otherwise, I wouldn't recommend getting stuck because then the difference between walking 4 miles to find someone or going home in a nice warm car will rely on whether or not your car goes into reverse. After much blabbering, my point is...you can live with just forward gears and an intermittent reverse. But, if you want reverse and have a few thousand you don't mind throwing at it, get it fixed. It should last you for the life of the car if you do (assuming you don't put like 3,000,000 miles on it or something) and then you wouldn't have to worry. It could be something else, like the linkage in the shifter, fluid or some crazy thing, but I kind of have a hunch it's not. I'm sure someone else will have a better idea that will actually fix it
Good luck.