Yes,I was daft enough to pay the massive extra premium to buy a TomTom 1000 as a TomTom Blue&Me2 with a load of functionality I dont need / use- but that's another story!
The mount pushes the top cover of the Option 68R downward. It engages by way of 2 side mounted clips,just below the "shoulder" which sits at the top of the port. There are 2x sprung buttons on the sides just above this shoulder to release these catches. Connection is via the triangular shaped projections at front and rear of the narrower section (that which goes in the port).
Difficult to clearly explain, but hopefully the attached pics will help?