While there are many kits out there, I would highly recommend against using one on your Liberty.
The reflectors in your headlights were designed for the light emitted from an incandescent bulb, and if you replace that bulb with an HID tube the light source won't be the same shape and location as it was with the original bulb.
This will result in poor light distribution patterns, blinding oncoming drivers and putting too much light on the road directly in front of the vehicle. While having more light right in front of you sounds good, it's actually not. It will impair your night vision and reduce your ability to see things at a further distance ahead.
Aside from the safety reasons, it's also illegal by federal law.
You'll find manufacturers claiming that their kits are "DOT" approved, but that's impossible as the DOT does not test or approve headlights. A "DOT" marking just means the manufacturer is stating the headlight meets applicable DOT standards. I can stamp "DOT" on a flashlight but that won't make it a legal headlight for a car.
"Is it legal to sell HID replacement kits?
NHTSA has concluded that it is impossible to produce HID conversion kits (converting a halogen system to HID) that would be compliant with FMVSS No. 108."
"Under FMVSS No. 108 Section S7.7 (replaceable light sources), each replaceable light source for headlamps must be designed to conform to the dimensions and electrical specifications for the headlamp source it is intended to replace. For example, if an HID kit is marketed as replacing an H1 light source, then it must match the H1's wire coil filament size and location, the electrical connector size and location and the ballast design for use with an H1 light source (which is impossible since there is no ballast). Consequently, companies that are manufacturing HID light sources (e.g., D1S, D1R, D2S, D2R, 9500, etc.) with incandescent light source bases (e.g., H1, H3, H7, H8, H9, H11, H13, HB1, HB2, HB3, HB4, HB5, etc.) should be aware that this light source design would not be one that conforms to FMVSS No. 108, and could not be imported and sold in the United States without violating Federal law. (The importer is treated as the manufacturer and subject to the same fines and penalties that apply to a domestic manufacturer.)"
Federal Motor Vehicle Safety Standard FMVSS 108