I have in fact pulled fuses apart to repair but keep in mind this using a sacrificial fuse to cannibalize the parts from. I'll be posting a couple pics of a Mustang that I did this to. I bought it at a swap meet for $40. Previous owner had modified it for electric and in doing so modified the firewall with a large opening to facilitate an electric conversion. He did a good job but I fly glo so I carefully removed it but just painstakingly cutting it away with a dremel. As I got close to the foam I then resorted to the razor knife and small saw. Removing the good firewall from a wrecked air frame was easy since the sides are blown out. so its easier to "chip" away the damaged stuffed heading into the firewall. I then dry fit it the other and when happy.....epoxy. The nice thing with E/Z is that all formers and parts are "keyed" so fairly easy. I also changed the former just behind the firewall and was just as simple as lightly prying it back and forth until the glue finally popped so-to-speak. the glue that E/Z used has been referred to as "hot glue". Let me tell you it is not. It "looks" like it and even has a slight softness to it but is in fact an epoxy based product. So most formers are easy to replace with some coercing and flexing and a lot of patience!
Now as for the seam you have to be very careful. If it has been fuel soaked or in the sun it is most likely brittle and doesn't stand a chance of survival. If it is not then your next challenge is the foam and not damaging it.
I have only been successful once at this and I did it with a heat gun slowly working the temperature up to soften the glue but not warp the plastic or melt the foam. I've never tried doing it cold although I have a feeling the glue could be "popped' loose as well with some very careful strategy. I thought about once bending an exact-o blade similar to the tool a car windshield repair guy uses to break the seal with....some what of a hooked blade.
Now the creases unfortunately will never go away. Again here I have managed to bring a little bit of a crease out with slight and slow heat but never come up with a solid method. Unfortunately the creases got the edge on me for now and I think that's just one repair that will always be elusive......just not meant to be.
E/Z knew what they were doing back in the day......designed life span so then you could just get another. These models were never meant to be repaired nor especially abused in the way you can a traditional balsa and film plane. They all flew well when set up properly but they had flaws there as well in the typical foreign translation to English barrier. CGs were printed wrong and instructions on a lot the models should be sequenced differently but hey.......that's the hobby....learn and modify as you go.
Hope that was some help
Paul