I would look at getting it repaired. If there is no communication but power lights up, it could be the internal SD card is bad. It still has to get sent in but it could be a very easy fix. No, Crestron will not send out a new SD card. I've had a couple MC3s with this problem and it was the SD card.

The PMC2 is NOT the way to go. Your PMC3-XP will work with any Crestron gear while the PMC2 will NOT. There's new firmware that will even allow a PMC3 to work with all Crestron gear.

Yes you should be able to put the camera's on the iPads and iPhones through Crestron. Yes you will be able to view when not at home.

If your programmer said to replace the PMC3-XP with Sonos or Heos, I'd be finding a new programmer right away! Neither will control your TVs, AppleTVs etc.