You can open up SSH from the Security button on the GUI. I don't believe plain telnet is supported on the new box. I would also recommend using Tera Term, Putty didn't want to seem to connect for some reason.
If you only have 1 interface for the appliance, just as a best practice, remember to block SSH from the outside world with a firewall.
ALT + F2 will open a terminal session.
I have never had a problem with PuTTY. It is what I always use. Except when I just ssh from another *nix box. I guess PuTTY is what I always use from Windows.
Yeah, I never had a problem with putty either, but on the new appliance I get: "Incoming packet was garbled on decryption". Any certain settings you are using?