OK, not to enter the 600 POO blow or not blow debate .... but... I rebuilt my POO RR ( 2 ) times .... one time we twisted the crank some f-in how...
Never the less... I would take a pass on a racer used . There is a reason manu's sell them to racers with no warranty. The race environment is the most extreme.( generally speaking ) It's not unfamiliar for many other race vehicles ( jet ski's, dirt bikes... ) to be purchased and sold at end of season. Since your looking for forum advice.... I wouldn't.
I do have a little time & experience rebuilding burn down's , maintaining sleds to 10k, fixing mine & my kids wear n tear and mishaps.... JIMO