So I had a TP lipo shortout somehow and go up in flames while in the car. it melted the chassis to the wires that go from the ESC to the receiver, so i had to cut them. This is on a Sphere comp esc. what is the easiest best way to fix it? Just splice on a new lead or try to open up the esc and resolder a brand new lead?

The easiest is a splice. Stagger the splices so they are not next to each other, solder together and use heat shrink. Soldering on the board in the esc can be tricky.

Any idea how the short happened?

internal short of some sort. Over the last couple months one of the cells would self discharge at about .01-.02 volts a day, so I had to keep a balancer on it at all times. I shouldn't of been running it but it still ran very strong and not puffed so it was hard to just toss out, plus it was a 125 dollar battery.

Thanks for the advice!