Logic Board Replacement Gone Wrong

Howdy. Help, please? Thanks. The short tale: bad spill damage. Corrupted logic board, but only partially. No local video, fried ethernet port. Everything else, including external video, survived. The replacement cost quoted me by the local non-Apple, Mac shop was more than I could justify on a year and 1/2 old machine. I'm handy so off to iFixit I went where a kind gent linked me to an inexpensive ($500) replacement out of Shenzen City. I have it, installed it but get nothing but the chassis power/status light when I boot up. SO, the first question I'm hoping the hive mind can educate me on is: post-logic board swap with everything healthy and in it's proper place, should the computer start up "normally" without any other software/format/etc. procedure? Second, my original board is an i7 2.8GHz model but the replacement is an i7 2.66GHz version. Would this processor change cause an incompatability issue with an already formatted machine? My gut tells me my too good to be true, inexpensive replacement board is DOA from China. Any guidance would be greatly appreciated. Have a great day.