cracked block in 5.7

[finer things]

hello everyone I have a 1987 SeaRay Monaco 210c it has been a great boat I bought it in 1992 and have done almost all my own maintanence but must have blown it last year and waited to long to winterize and cracked the block there is water in the oil I am not a mechanic but I am considering swapping the engine is this something I might be able to do myself otherwise I dont know if its worth the money to have a marina do it any suggestions would be great