Hello!
What sims were you into upto now? Anyway, better late than never; so welcome to LFS!
As for you second question: yes, it is possible, but due to the nature of the shifter on the G27 it would be awkward to use. The G25 had the built-in shifter as you might be aware of, unlike the G27.
What you could do is assign shift up and shift down (in Options>Controls>Buttons 1) to the shifter's 3rd and 4th respectively. So when you shift into 3rd it would go up a gear. But obviously, the shifter would stick in 3rd, so to shift up you'll have to shift to neutral and then shift back in to 3rd to go up another gear...
Don't forget to change the gear shift mode to "sequential" (Options>Controls), or toggle the gear shift mode with shift+G, or it would not shift...
Hope to see you on track!