How often does problems with transmissions occur for this make and model? on 2006 Buick Rendezvous

what would the most reasonable cost be to replace a transmission and what kind of maintenance would be best to avoid this problem?

Asked by for the 2006 Buick Rendezvous
the trans replacement could cost approx 4000.00 and the best adv is service every 35k miles to avoid this issue again