How much acetametaphine is TOO much to take at a time? What are long term affects of ingesting some every day?

Is it OK to take 2 Percocet 5 mg AND take Tylenol Severe Cold? I'm sick but also had a normal bout of pain, but I was afraid to ingest both because that's a LOT of acetametaphine. How much is too much? I don't want to OD.