TRANSOM TROUBLE?

[STRIPER2828]

MY 1975 20FT MA IS IN MY GARAGE ON BLOCKS STRIPPED AN BEING SANDED TO GET READY FOR PAINT. I REMOVED THE ALUMINUM CAP ON THE TRANSOM ,APPEARS THAT THE OUTSIDE SKIN HAS DELAMINATED AT THE CORNERS OF MOTOR WELL,THREE OF THE FOUR ENGINE BOLT HOLES APPEAR SOLID THE FOURTH HAS ALITTLE ROT IN THE BOTTON. I REMOVED BOTH MOTOR WELL DRAIN TUBES AND TUBE AT BOTTOM OF TRANSOM,WOOD IS SOLID BUT WET. USED BOAT ALL LAST SUMMER AND TRANSOM SEEMED FINE. I HAVE A NEW 175 OPTIMAX IN THE CRATE FOR THIS BOAT SITTING ON THE FLOOR,IT IS A 20IN SHAFT MOTOR. ONE SHOULD I REPLACE TRANSOM.TWO SHOULD I RAISE THE NEW TRANSOM TO 25INCHES AND EXTEND THE MOTOR SHAFT. THREE IS THIS SOMETHING I CAN DO MYSELF. FOUR IS THERE SOMEONE OUT THERE THAT CAN GUIDE THROUGH THIS---PICTURES,DETAILED INSTRUCTIONS,COMPOSITE OR WOOD ETC. DOES THE EXTRA FIVE INCHES IN HEIGHT REALLY MAKE A DIFFERENCE ANY INPUT WOULD BE GREATLY APPRECIATED