Welcome back!
If you want to be somewhat competitive then you'll probably benefit alot from a brushless esc, brushless motor and lipo battery setup and maybe a new car too as not sure if the cougars drivetrain can handle the high power motors we put in are cars these days
The lipo battries you never have to worry about discharging and conditioning etc. ever again and you'll only need one per car for club racing as you can just top it up after each race although you can run them for 2 or 3 runs easily without charging them so makes life alot easier, alot of people never even take the lipos out of their car. They also have alot more punch/power and capacity (up to 5500mah) than the nimh counter parts and are alot lighter too so well worth it.
The brushless speedcontrollers and motors are basically the same... less hassle... You don't need to do any maintenance on the motor, they are more efficient, more powerful etc etc...