I know this is not want you want to hear, but please send it to Polar. Do not jeopardize a $300+ unit. I would not get it wet. For those of you who visit Boston or NYC Marathons, you will the that glass bubble chamber that all watches go into to insure no possible leaks. I know it is 4 screws and an “O-Ring” but you are closer to destroying your watch than repairing it with a Radio Shack battery.
I just sent mine back to Polar this week for battery replacement. I took it to a BatteriesPlus store here and they said that it needed to go back. I couldn’t even tell how to get inside the thing!
You never know what’s in the Polar pipeline in Finland!! AS for the RS800, with GPS you could switch the RS800 from min/mile to mph and ride with it. Since it is a running unit and not a true tri unit, it will not switch from mph to min/mile without stopping it