It would help if we new what you were re-powering , what model engine is now installed and what you'd be replacing it with? Could you get away with a rebuild?
My latest re-power cost me around $600.00 (2.5 Suzuki) on my 17' daysailor.
My old 27 foot Watkins with a 2GM cost me around $2500.00 for a rebuild.
You start sailing with a bag full of luck and an empty bag of experience. The idea is to fill the bag of experience before you empty the bag of luck.