The Paragraphix PE set is pretty much standard for the Refit these days, but PNT and Green Strawberry also have similar offerings.
Lighting kits are available through Starship Modeler, Big Easy Modelling Solutions, Starling Tech, Tena Controls, and Madman Lighting.
Advice? The refit Connie is labor intensive to get her to the point where you can light her up, because she was not engineered to be lit. Take a look at the saucer walls for proof of that. A lot of milling, drilling, carving, and sanding are needed to open up the pylons for wiring, prepping for raytheon, opening the photon torpedo bay, and so forth. The plastic is a bit goofy in that it mills better than it cuts, so get a couple of different sized cylinder burrs for this initial work.
A lot of circuits in this - a variable bench power supply is a huge help. Test constantly, particularly if this sort of electronics work isn't something you're used to doing. Once things are sealed up, circuits or components that burn out are hard to replace, so test the rig, then test it again before you commit to sealing things.
If you buy individual components, take the time to plan the wiring harness out on paper before you build it. Once things start coming together, you realize how little room there actually is inside the model. An ounce of planning saves a lot of headaches - know where your wires run before you create a nest of loose wires because there are a lot of windows.
Goofy plastic - clean it thoroughly, then clean it again or the oils and heavy mold release will mess with you down the road. Light block carefully because it will pick up light and glow like crazy.
Building a jig to hold things steady is a huge help - big model with a shifting center of gravity, so it really helps to be able to lock it in place.