Hopefully you'll get lucky. It depends how much they want rid of it.
If you look at the steering pump in the upper helm there's usually a plug, if you remove it and very gently fill with ATF fluid, once it's full turn the lower helm slowly from side to side, as the fluid level goes down top it up, leave just a tiny little bit of space to let the oil expand when it gets warm.
IF, and I'll keep my fingers crossed you can pull it off and you need to pressure wash the bottom, get yourself some disposable paper 'Tyvek' overalls, a face mask, light rubber gloves and goggles and start at the keel and work up to the waterline.
Many start at the waterline, if you do, the water will be running down your neck when you get to the keel.
The reason I would be inclined to urge you to do it yourself is that you'll see any imperfections in the gelcoat.