1, is300 lights wont fit the is200 with out a lot of body work, so not worth the effort IMO.
1a, the self leveling feature is fitted to the suspension not the headlights, and thats a huge job to under take.
2, i'v had hid's fitted in my is200 high n low beams for the past 4 years without any issues and i bought them from ebay.
3, fitting hid's to your fogs light is easy, remove the fogs, there's enough cable to connect the hid's to the loom without removing the bumper,add some lengths of double sided number plate tape to stick the ballasts to the car and refit the fogs.
HTH.