A1) Yes, you just need to be careful as a heatgun tends to take sintra from hard to gooey in a few seconds. It also changes the surface texture so be sure to heat the back side.
!! A heat gun is much inferior to hot water for basic molding!!
A2) Cyanoacrylate Glue (aka super glue) is really the only choice. Just be careful since the edges of sintra are porrous (sp??) and the thin superglue can transfer between edges in the pores. Keep some acetone (nail polish remover will do in a pinch) in case you glue yourself to... yourself. 