replacing rod bolts

When is considered time to replace them?When the engine was cheapy rebuild the first time,I installed new rod bolt nuts from the dealer.the engine leaked oil badly from the cam plug,so the engine only had 300 miles on it.It is now sitting apart waitting for it's next adventure.And if it is considered replacement time,any tips for doing this at home?If it matters,the engine is a 73 360 from a 3/4 pick-up,has 125,000 miles on it,always a 2-bbl intake/carb,with the rebuild it got a 340 cam/springs/headers/dual exhaust.Thanks!Bob