Watch winder motor replacement - help please

[eastsider]

Guys

I have a winder like this one:
http://www.ebay.co.uk/itm/-Watch-Winder-Diplomat-R...

the motors can barely turn the winders anymore. I want to try and replace them but not idea how to get into the workings! The bottom half of the box is solid so it must be through the inside some how.

Anyone done this / got any ideas on where to start without ruining my winder?

Thanks in advance!