Nice one, wish I had workmates like that.
If it has bearings check and clean them, if it hasn't, get a full set of bearings in it.
Give the whole thing a good check over for loose screws etc. so that you can fix any potential problems on the bench at home rather then try and work out where that wheel went and why did it fall off.
As to motor that is up to how fast/hard you want to drive it but remember the harder you are with it the more expensive it is, the fastest motor I own is 19T and I havn't even used it this year, most of the time I usually run standard, sport tuned, GT, or Dirt tune, it depends on which cars I take out with me. My super sabre (basically identical chassis to hotshot except twin rear shocks) is alot of fun with a sport tune and in all honesty much faster and the 80's design suspesion starts showing its age.
Cheers
Hamish