when stripping graphics off the petrol tank do i need to drain the tank first

a few months ago i paid £500 for a mk 2 crm 250, this is only my second bike, and i feel its stupidly powerful for someone with as little riding experience as me, being only 17. as a result i hav had loadsa falls, most were going slowly :oops: , but i had 1 high speed crash and hav a lovely big hole...