This is a really old thread but I just got around to doing it on my e70 and thought I would share my experience...
I cut off the original AZ sun faded headlight lenses from my e70 and replaced them with $50 shipped Gplus versions from an ebay seller.
Getting e70 headlights out is a real PITA. It requires pulling the inner fenders, and fighting to get them past a support bracket. Then cutting the old lenses off and getting them prepped also took quite a bit of time. Cutting the lenses off requires a lot of patience, it is easy to cut into the inner gray trim or even the angel eye if not careful (I nicked an angel eye but it wasn't bad enough to matter)...
This was a ton of work. The original BMW sealant is more like silicone than butyl... I was able to get the new butyl done with just a heat gun rather than an oven. I didn't see the need for putting the whole thing in the oven when some careful work with a heat gun to heat up the edges worked just fine.
Here is one side, the spec in the lower right isn't a defect, it is a reflection or spec of something on the outside.
The new lenses (and my other cars) are getting lamin-x film ASAP. Never let them get this bad... I probably could have sanded them out but I thought that the $50 housings were a great price and would give a better result. They probably did but it was also more work than sanding them...
I did have one major setback that required rework during the process that I wanted to warn about...
I got tired at 2am and when I assembled the driver side and got it all done and realized that the outer edge of the inner gray trim wasn't aligned (the tabs weren't engaged so it looked really bad). This meant I had to pull it all out again, re-heat the new butyl, clean it up and add new butyl but at least that is possible with the butyl unlike the factory sealant.
-Rich