If I switch my .9's for 11s or 12s, will I need to adjust anything?
You'll have to adjust your intonation. If you have a tremolo, you'll have to add springs in the back, too.
Yeh, intonation, tremelo tension if applicable, and with such a guage jump it is recommended that you give your neck a bit of a tweak, there will be a noticable backbow which is better off fixed than left. Also, flog the hell out of your fingers untill they adjust to the guage, it takes probably a solid week to beef up callisses
Thank you guys =)