The bike I just put together has one of the seals inside the bearings. The left one is outside the bearing. I freeze my bearings before putting them in the case. And, like you've heard, many people them freeze the crank and heat the cases before putting the crank in.
Well, I don't. I'm like you and afraid to subject my seal to the heat. I did freeze my crank, but then, put it in and simply tapped the cases with rubber mallet until I could get the case bolts (screws) to catch. Then, I went around and slowly tightened them in the correct order.
Works like a charm every time, but I'm sure there are experts on your bike that have the perfect answer you need.