If you search there are a couple of threads on how to open similar units. You twist them along the length untill one of the catches releases then use a very small screwdriver to finish the job (at each catch). I did this once with a MX-700 and it worked, but I ended up damaging the case (not bad, but there you are). It's very scary (you would be surprised the amount of pressure required) and I suspect the odds of damaging the unit are very high (fragile plastic etc). Do at your own risk... These were probably not designed to be repaired (or they assume the case is a throwaway and don't worry about it). Be sure it's completely dry before inserting the battery. I suspect URC would be sending you a new one (probably cheaper) as a replacement.
Please note: On my 980 it feels like there are two screws which would have to be removed first. One in the battery compartment and one behind the display. Both are under labels but you can feel the holes underneath!
