Yes, heating the frets with a soldering iron makes removing frets much easier.
If you plan to scallop the spaces between the higher frets, it may be an idea to do so prior to removing the existing frets, which you can use as guidelines. If you mark the old frets whilst scalloping, it will be less of a problem than marking the new ones. Of course, something to take into account will be if the new frets are wider to leave room to seat the new frets.
An alternate would be to remove the frets and make sure you know how much width you need for the new frets and then use some protection either side of the space you intend to scallop, with some thin metal and masking tape for example and do the scallops then install the new frets.
I suppose if you have some scrap wood, you could cut some fret slots and practice some scalloping with or without frets installed.
There are lots of other tips etc, related to fretting too long for this post.