new Servo

[gravel rash]

Hi all

I'm currently running a sanwa exzes 40 mhz radio. I was running a ko fet 2015 servo and guess what, its blown. I would like a new servo similar in spec to that, but not sure if the new digital ones will run of my receiver.
I read on here about bec what ever that is.
my esc is a gm v12 running a gm 13.5 triple motor in losi xxx.
I know its old school i have been out of racing for a while and im getting back into it.

another question, are stick lipos the same size as saddle lipos.
Im thinking of upgrading slowly to the brushless setup, and ive always run saddle packs just incase i decide to change cars, i dont need to buy new batteries. with the old ni-mh they were the same size in saddle pack as stick pack.

thanks