I can't answer any of your questions, I'm just part of the "Welcome to MintPPC" contingent--a big hug to you . . . . OK, goodbye now . . . . : - ))
Actually the only question I can answer would be, the "easy way" to find applications, such as email applications, is to use "Synaptic Package Manager" and type the name of your app into the search window; if there is a port for your system it will show up there and you can click "Apply" and synaptic will install it and the most needed dependencies. If it doesn't show up in synaptic, you could do it the "hard way" and compile it, but I really don't know how to do that.
Icon buttons might be in "system settings" or try right-clicking on them and see what hapens . . . .
iBook G4 933 MHz 640MB SDRAM [14e4:4320] BCM 4306/3 b/g. xorg config: http://mac.linux.be/files/xorg/ibook7.txt--MintPPC11
iMac G4 800 MHz 512?MB RAM http://www.everymac.com/imac//imac_800_fp.html