Replace Mercury Vapor outdoor lights

I recently bought an older home in Texas that has mercury vapor landscape lighting. The lighting in the front yard doesn't work and trips the breaker, due to what appears to be a bad ballast on one of the lights.

I would like to replace these lights as they go out with LED bulbs and while I'm comfortable with electrical wiring indoors, I can't seem to get a clear answer on the outdoor wiring:

I haven't used my voltage tester on it yet, but I presume the wiring coming into the ballast is simply 120V and to convert a light from using mercury vapor bulbs to LED bulbs I would simply just re-wire/remove the ballast so the LED is running direct on the 120v line, just like an indoor light.