[villagetinker]

The light kits tend to be standardized, so Lowe's Home Depot, and probably ACE will be able to help. Now having said that, there are some potential gottchas, first, remove the bottom plate on your existing fan, and look at the connector, I have seen 3 different types, you will want a matching connector on the light kit. Take a picture to check the light kit. Second I have seen some light kits with unusual light sockets, try to stay with standard Edison base or candelabra sockets. The light kit should come with 2 new pulls, one for the fan and one for the lamp, check that these are actually labeled (and install correctly). Finally, some of the kits have only one chain color which may not match your chain, the end cap at the store should have matching chain.
I have done this several times, the new extension will match up with the holes and the diameter of the plate you removed, the light kit will plug in, and once the screws are tightened you should be good to go.
One final word of caution, depending on the builder, the BLUE wire at the TOP of the fan may not have been connected, if this is not connected, your light kit will not work. Also, if you are really lucky, the fan was wired with a additional RED wire in the cable from the existing wall switch. You can connect the RED wire to the BLUE wire, and change out the existing wall switch for a double switch and then have one switch for the fan and one for the light. i did this will all 4 of our ceiling fans.
I hope this helps.