When to get fitted professionally?

I say go for it. The point of fitting is to get your clubs to work with you regardless if you're swinging good or bad (especially when it's bad). Now would be the time. The bigger problem I think you'll have is with you: you'll drive that far, and the whole time you're going to put pressure on yourself (because of what you've mentioned). Most likely that'll wind up screwing up your first attempt, which will lead to a downward spiral. Go in loose and have fun with it. Just hit it- I bet you'd be surprised.