electronics

[ Hi, i am new to hobby, I have had some successful prints, I built an enclosure for the printer, when hooking up the electronics, I crossed the + and - 12volt lines to the board and I think it is fried, ext does not work, bed heats up without selecting, lcd is blank etc. My question is replacing the board (a Melzi with Marlin.) If I were to purchase a board such as the one in the attached picture, would it work out of the box or is there more to it ? I cannot get any response from the seller.
Thanks for any help you can offer.

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would it work out of the box or is there more to it

no you gonna need to configure and upload the firmware,,,, am no fan of those red RAMPS board, a good alternative for the price is a mks Gen l you still gonna need to get stepper drivers.

Or just get one with built in drivers, they perform better.