Re: The new guy
Every answer you get is going to be different as most things are subjective. Almost any bike can be converted. I converted a 24 inch girls schwinn as my first bike build.
The only kits I am familiar with are the china kits that go inside the frame. I don't think there is a lot of difference in them frankly.
Ebay is where I bought mine and I would recommend it as most dealers who sell there also have website where they sell their kits for a high price.
Twenty five to thirty five is reasonable personally over twenty and I get nervous but I'm old and my balance is not all that good. Lots of guys zoom around. When you get your kit come here for instructions on how to install it properly lots of guys here are more than willing to help.
Welcome to motor biking.
My posts have entertainment value only. A bike ain't yours till it has your blood on it. Then it owns you.