Yes, you can definately use an oven to do the job. It is all depends.
For me, I used 150 degree and check it every 5 min to see on whether the sealant is soften and melted. If not, put back for another 5 min and check again until you can separate them apart.
Be careful and don't just leave it in the oven without supervision, you will easily melt the lense as well. I experienced it when I tried to install an agel eye for my Hyundai Sonata.
After more than 10 times experiences in opening my headlights for both on my cars. Now, it is just a piece of cake.
My suggestion, do not use silicon, use the windscreen sealant.
Final suggestion, use gloves. You won't want to burn your hands.
GOODLUCK!!!