1) On the old 3DS XL with the latest version, there's currently only two options to hack the console: hardmod). For this you need equipment for soldering. The other option is DSiWare) that requires a specific game (out of four) that isn't sold anymore and a second 3DS that is already hacked.

If you can do neither of these two, just sit tight. developers are currently working on a new hack called "ntrboothax" that will only require a magnet, a DS flashcart and a powersave to hack on any version.

2) All 3DS have a yellowish tint on the screen caused by the glue used in manufacturing but this should have disappeared over time when the glue dries up. If you bought the console close to the release, there were some issues with this batch of consoles and the yellow tint is more visible. I have heard that higher brightness on the consoles makes it less visible, but you can't really fix it unless you want to replace the screen.