2011 impala still acting up after Crank Shaft Position sensor

I don't know if this is the right spot, please direct me to the right one if not. I read a lot of forums about the crank shaft sensor but they didn't answer my question witch is... I changed the crank shaft sensor in my 2011 3.5 Impala and it's still hard (even harder) to start, runs rough & no RPM gauge, so with out the rpm gauge I can't re learn it, So I don't know what to try next, Do you think I might have got a faulty sensor? or would you look some where else?