Charging the AC System condensor replacement

I replaced the condensor on my daughters 97 Lumina. I charged it with three cans of 134A, one of the cans contained 2 oz of oil. Its running OK but a friend told me I will damage the compressor because I did not put a vacuum on the system before charging it. Is this true???

Could be, the system should be evacuated before recharging, also the condenser should be drained of oil the amount measured and the same amount put back in the system, ac repairs really require some specialized equipment and training.