y don't you mark the inside of your top panel with all the hardware inside? then you'll know where everything sits. easier for you to place to fan in the best position. and since its your first time modding. better be careful. handling power tools can be dangerous. don't rush into cutting and be very sure that there is where you want to cut or drill. sorry.. i'm nagging u aren't i?

there must be a way to touch it up nicely..