The reason why I asked the questions is that the 1840 has a pretty solid drive chain set up, including the motors. A 'stripped' spline on the motor, sounds very unusual.
Have you actually spoken to the dealer about this? There are questions to be answered before you could really commit to buying. A motor for one of these is around $1800 - $2200 US & there are a few different options re type. Depending on serial number, the drive motor may be obsolete & TWO new ones will be required to make it drive properly..........
Like I say alot more information is required :drinkup