I had a quick look at the manual for the ESC and found it is rated for 7 cell - 8.4v .
A charged 2S is 8.4v so its on the limit with no buffer .
There is no Low Voltage Cutoff for lipo ( there is a cutoff , but too low for a lipo ) .
You could fit a Lipo Low Voltage Alarm .
Personally , I would run a 6 cell Nimh as I dont know how the old ESC would handle the Lipo .
Flysky GT2 is a basic Transmitter + Receiver .
IMax B6 charger will do all your batteries . They have AC and DC types , get AC if you want to charge at home .
A Deans connector will do the job , cheap and easy to solder .