1/8 conversion beginner questions

Hi,

My RC experience is with mid sized electric helicopters and unpowered gliders. I was into cars years ago with my last buggy being a 90s RC10. Well the car bug has rebitten me and I'm amped to do a 1/8 buggy brushless conversion.

I've been trauling this forum and have seen some of the other setups you guys are running. Some really awesome setups!! I have quite a few questions and would hugely love to hear from the experts here.

After what I've read here and elsewhere, my eyes are currently focused on a Jammin X1-CR FTE kit. How is this buggy? Are there any difficulties in converting it? Any better recommendations?

Being into choppers I have some electric equipment that I'd love to reuse if possible. Will a Hacker C40-12L on 4S with the right gearing be big enough to get me going? I'm not aiming for high speed at first, so gearing way down would be fine.

Assuming the Jammin X1-CR, what are the gearing options? I haven't found many references to the kit's bundled gearing, but it looks like a 48T main with 3.3:1 on the diffs. Is it fine to stick with the stock gear train or does it need to be beefed up? Anywhere I can read up on gearing options? How can I find out the pitch/module of car main gears?

I see many references to a machinist called Mike. Is this the owner of RC-Monster? Does he formally do custom machining?

Thanks again for reading this far! All advice appreciated. :)