If I buy a pre-lit tree, will all the lights go out if only one is bad? How will I know which one is bad? How can I replace the bad bulb?

All prelit trees today have a shunt circuit in the bulb so that if it goes bad, the rest will still work. Sure beats the old series way of wiring and having to run a resistance check to see which one was bad.

Oh man... the old days of having to try to figure out which bulb is bad. Can't say how many strings of lights I simply threw out to avoid the trouble. Anyway, modern lights and pre-lit trees don't go out with a single dead bulb. Just the bad bulb goes out and the rest stay on.

My dad would pull the lights out and start testing and by the time it was all fixed Christmas was about over.