Im pretty sure the bumper and head lights are directly bolt on. The fogs will bolt into the bumper. As far as HID's go, id say go with one of our supporting vendors kits, we know they work and theyll prob be cheaper than the OEM kit.
Heres the site for AAC's OEM Headlights
2005-'08 Chrysler 300C OEM Headlights
Heres the site for OEM Headlights, Fogs, and wiring harness. This will for sure give you everything you need for the conversion as far as lights go
300 Base, Limited, & Touring Model to 300C Conversion Kit
I hope this helps, and im going to be doing this conversion too, so let me know how it goes!