I have a Harbor Breeze model 7850544 ceiling fan with the 3 little lights. They don't provide much light and I'd like to change the lighting part and keep the fan. Can I use a ceiling fan light kit or is that only for fans that aren't purchased with lights?

Most light kits are interchangeable.

As long as the fitting is the same diameter, you can use pretty much any light. They usually screw to the fan base adapter with 3-4 screws. Once the light is down, there will be 2 wires, black and white. Make sure power is off and remove the light ***'y. Take it to HD or Lowe's or a lighting supplier and match the base size and screw pattern for the one you may want. Reverse to reinstall.

Guess I won't abbreviate assembly again!