What is the history of the crank? Both before you got it and after. If It has been beat on a lot, no way would I just fix and go. They do crack and break at some point.
From friends experiences, at 550 hp the average life of a good unabused stock crank with stock bearing sizes and lighter than stock pistons was about 1,000 to 1100 runs. If you think you are over half way there, might be worth the $$ to upgrade. Only you can make the call.