I fitted some cheapo chinesium hids in one set (still got another set waiting for Fred to get back to speed with his next run, hint hint...
... )
1. Didn't actually have to take too much off the bowl, just a kind of semi-circle out of the middle on the 90 degree bend where it transitions from upper to lower reflector half to get the lamp in there. Just take the shroud off and keep shoving it in the hole, dremmel a bit more, shove again etc till it goes (real finessed like). I did take a bit too much off the first one I did and went right through to the other side, but luckily it's hidden back there so a blob of steel putty closed that. I had to take a lot more off the shrouds than off the bowl... that was major chop work.
2. Not sure what hole you mean?
3. Man you guys are lucky with your huge ovens, no chance of fitting them in my tiny apartment oven. Had to open them with a hot air gun and close them up with Permatex black silicone and a couple of clamps.