I would toss sensors in there, as if you actually end up in some snow/ice, it is harder to tell while driving if a pressure is getting too low, and 4 sensors are probably cheaper then a new tire.
Aftermarket are fine, make sure they're 315MHz, and compatible with the system, most parts distributors can tell you this.
Aftermarket are fine, make sure they're 315MHz, and compatible with the system, most parts distributors can tell you this.