Just ordered tekin 2050 buggy system

[rcobscession]

Just recieved my combo but i realized it is the 2650 instead of the 2050 that i ordered. I am going to keep it but i really need advice on two things: 1.. will the reciept saying one thing and what i got keep my from getting it serviced if need be... If so i will exchange it? 2... I had plan on running 4s but i think that might be to much for the 2650 motor as i here on 4s it is uncontrolable and really to fast to race with and i am uknown as to what pinion i should use with 4s. Please Help?!