Generally, if you are renting a reservation from a member, they will send you a copy of the confirmation that they receive from
DVC.
However, you will not be able to contact DVC Member Services to independently verify the reservation. They will not speak to non-members. DVC and Disney do not get involved in the rental process in any way, shape or form. Renting is a private transaction between two individuals.
Some members have reported that if they contact the resort a few days before check in, the resort will have the reservation in their system and will confirm it.
There is also no way to 'protect' against the reservation being cancelled. The member retains full control of the reservation until you check into the resort, and can cancel it at any time.
I know that sounds scary, and that it isn't what you wanted to hear. The good news, is that the great majority of DVC owners are honest folks, and the great majority of rentals go off with out a hitch. We very rarely hear of problems with rentals.
It just emphasizes the importance of understanding the rental process, and trusting the person that you rent from. You can save a great deal of money by renting, but the tradeoff is that you don't have control of the reservation. For some folks, that level of risk is something they'll never be comfortable with, and renting isn't for them.