GARMIN GPS masquerading as a BMW NAVIGATOR V

Coming to this forum in the hope that I might find somebody who can help me fix my BMW Navigator V motorbike GPS.  you may or may not know that these expensive little gadgets are the *** offspring of BMW and GARMIN, an unholy alliance if ever there was one.  I believe it is basically a Zumo.  A Zumo battery from a Garmin shop is $59.  BMW slightly modify the plug end and charge $135 for a battery.  These are a great device for we motorcylists, with glove capabilities, integration into the bike's controls and sound system etc etc.... BUT .... when it comes time for dealer support BMW point me to Garmin and Garmin point me to BMW.  I wouldnt buy one again, but I now have this handy gadget and want to keep it.  

Recently, on a trip to Jindabyne where it sat on the bike in the cold overnight, it stopped working.  Once we all thawed out, the battery would recharge but wouldnt hold it for long.  I changed the battery and the device worked well, but when I tried connecting to my laptop and Garmin express, it wouldnt recognise the device.  To cut a long story short, the device now wont even start up. I dont want to waste time with the dealers any more.  My question to the forum is .... can anybody recommend a good techie ?   My computer industry background tells me it needs to be wiped and reloaded and all will be well.  There must be somebody who knows these things back to front and can play with it.   It's too good to throw away and I dont want to be left with a hole in my bike's dashboard.  I am happy to go anywhere in Sydney or the South Coast to meet my Garmin guru and happy to pay for his/her help.