it'll differ from WJ to WJ. Some have issues, some don't I've one harness it didn't like, one it's fine with. Your choice. What it basically is, is a capacitor so the HID's don't flicker, etc. the retrofit source has a mopar specific harness for this. Regardless, you HAVE to have a harness to run HID's.
10,000k bulb is useless. You lose your light output for sake of pretty unicorn purple colour. 4300k or 5000k as said is what you should use. Even 6000k you lose light output. 4300k gives a more yellow halogenish colour, 5000k gives a white colour. 35watt is all that is needed. You don't need to go 50watt, and in some cases depending on how used can melt plastic housings (ie home made foglights)
Now with all that being said, DO NOT EVER PUT HID'S IN HALOGEN HOUSINGS. You endanger yourself and everyone else on the road. Some municipalities like one near me, actually will ticket you. Halogens work in a particular way and halogen projectors and straight housings are designed for that type of light and how the bulbs are designed. HID's work in a totally different way, as well as being up to 10x brighter. This is why glare is such a big issues. The bowls on HID project light differently and are designed for how the HID bulb is. Take a look at the salts in an HID bulb, and the filament in a halogen. It's quite obvious they produce and emit light totally differently. Now HID in halogen projectors aren't quite as bad, but they still give off glare, but in a different way. Search on google images and you'll see tons of photos showing what happens. As for colour? the blue many think and try to get with different kelvin temps is actually the flicker which is directly due to how the HID is and how the cutoff is that controls how the light is sent. My 5000k gives a bluish cast at the top middle of the cutoff shield. This is indictive of HID's. The best way of doing HID's though is a proper retrofit with projectors that have been tweaked and engineered to get the most out of HID lighting. Most go with the FX-R bi-xenon or mini H1's on the WJ's I've seen.
The other important thing is don't cheap out on bulbs. They are more important than the ballast that runs them quality wise. Cheaper bulbs are more likely to have a greater/noticeable colour shift and don't last as long. Other things is HID's come in only a few sizes. Anything that fits typical halogen housings have been rebased to fit and passed off as a 'plug and play' which really doesn't exist.
Me personally am running morimoto bulbs and ballasts through the retrofit source. Great warranty and haven't had any problems. I've now done three retrofits, and have been dealing with them for quite a while now. Great customer service, will help you decide and design what you want and what you will need, and great warranties. And no, I don't work for them LOL I do like a business who cares about their customers.