A couple of things... I would agree that servicing the fluid wouldn't hurt, other than the cost of the fluid. I would go with Valvoline Maxlife ATF as it is much cheaper than NissanMatic "S" ATF and works just as well. As far as being "burnt," does it "look" burnt only or does it smell "burnt?" The reason I ask is that NissanMatic "J" and "S" ATF typically "look" burnt when it's drained; it's usually a dark brown color for whatever reason. On the dipstick, it is almost clear in color or "pink-ish." NissanMatic "J" and "S" are synthetic ATFs and it would take a great deal of heat to break them down. Since the failure is in reverse, I would suspect a faulty reverse solenoid on the valve body or a bad reverse clutch. The reverse solenoid is hard to find by itself; one usually has to purchase an entire valve body. A bad reverse clutch would mean the transmission would have to be removed and disassemble, so it would make sense to overhaul the trans or replace it with a reman unit, at this point. Nissan uses reman units on almost all of their vehicles as replacements as the cost of rebuilding is generally not practical. If the fluid is actually burnt, then something failed and caused it to be that way and typically an overhaul or replacement will be needed in the not so far off future. It's also almost impossible to get all of the burnt fluid out of the trans, even if it is flushed. Last, sometimes things just break for no apparent reason and not necessarily due to a lack of maintenance. Anything mechanical can fail before it should; it's just the way it is sometimes, unfortunately. Most people have gotten pretty good service out of the RE5 transmissions (so long as the fluid didn't become contaminated).