do you have to buy an entire brake light assembly for one LED bulb that is out on my brake light?

 

Unfortunately yes unless you are electronic savvy and can solder.

 

It's pretty hard to solder SMD LEDs by hand. Even if you can solder and use a voltmeter to do the wiring yourself, you still need to make sure the new LED is compatible with the old LED driver.

Much less hassle to buy a whole new brake light unit.

 

The brake light LED ring can be bought separately from the entire light assembly.