1) Depends, mostly will be 2 - 3 days, depending on what time
you went down to NCC
2) Use Nokia PC Suite to try back up your msgs and contacts. MMC
can back up your contacts too.
3) 1 year from date of purchase.
Btw, LCD are not covered under warrenty, so even if your phone is
still on warrenty, you will still have to pay for the LCD costs if
its need to be change to a new 1. And the LCD cost about $76 +
repair charges about $24 = total about $100. How I know? Cause my
N3230 LCD cracked before, and I dunno how it cracked cause it
happened overnite. Morning I woke up, see got crack le. 
Oh and if they change a new LCD screen for you, the warrenty for
the new LCD will be 2 or 3 months.