You'll arrive/depart most likely to/from the C terminal. No "int'l" vs "domestic" gates at C terminal. You'll clear immigration at Dublin heading west, so no need for "sterile" int'l arrival gate. UA is solidly middle of the road in terms of service in Polaris. Don't expect much and you won't be disappointed. It's not Emirates or Singapore, but it's not Air Koryo.

I just checked flight status today and it looks like your EWR-BOS flight may depart from Terminal A. I don't know if one has a means of staying airside in the transfer or if one has to exit C and go through security again at A. There may be a bus transfer airside, but I don't know (and I'd like to know, for future reference - anyone?)