IIRC, EWR doesn't have an IFL in terminal C - remember that EWR is a pre-merger Continental hub, and Continental hasn't had an international "First" service since the very early 90s. IFLs are generally found at pre-merger United hubs like SFO or ORD.
If the OP is flying an all-UA itinerary, I'm afraid they're out of luck in a number of departments:
1) You're going to be limited to the United Club locations in Terminal C. There are LH & SK lounges in Terminal B departures, but because EWR is not fully-interconnected post-security, you won't have access to those lounges.
2) Only UA, US, *G or a GlobalFirst/BusinessFirst ticket will get you into the United Club for free. (I think there might still be a level of PriorityPass that will work as well - I think it has to be a paid membership, and not one provided as a benefit.)
3) Don't expect anything approaching luxury in the United Club, although there are showers available in at least one of the clubs in C. (You can find more detail on this in the UA forum.)
BTW - SFO-EWR should only take about 5.5-6 hours, tops. Remember to account for the time difference between Pacific (GMT -8) and Eastern time (GMT -5).