Sounds like you had a tough time, if i were changing the piece i'd just cut the nut off with grinder or air chisel, if i had enough working room to do it without mangling anything else.
1. The ball joints are pre-lubed, or should be anyway. If they've got a grease fitting i'd grease em anyway for good measure though, do it till you feel or see the rubber seal swell and then stop greasing. 2 or 3 pumps should do it. Dont overgrease or the seal can break and that you do not want.
2. If the parts look wrong, they might
be wrong, as you suspect - most parts are pretty much identical to the parts they replace, of course. A,t the least id call the parts people you got em from and have em double check the number (even though this is no guaranty, auto parts companys can and do make plenty of mistakes like everybody else).
Hard to go wrong with NAPA parts i have found. (And no i dont work for them)