I took my 2013 3500 tradesman for some recall work and my service airbag message was on. Dealer said the airbag control module has an internal fault and no way to tell if anything else is wrong. $850 for the module no guarantee it will fix the issue. I see some eBay postings for used ones under $100.

Anything I should know or tips before buying one? Or maybe a good source for one?
Are they plug and play?