Leapt in hear a couple of days late, (spent a week in Greece on holiday) point to note, if you have the proper batteries, pull the board with power off, stand it on an insulating surface e.g. bit of cardboard or the like, remove old battery, fit new, all should remain. Parameters etc will remain if you take a very short time to change the battery as the discharge rate of the capacitors is relatively slow, hence quick change no data loss. Fit the battery the wrong way round (one of my blokes did this) you will lose everything.
GEM