Yes, the first time you experience a classical migraine it can be quite frightening.
In response to your questions:
1) It may or may not happen again, only time will tell.
2) It is a little strange that you are experiencing it for the 1st time at your age, but it is certainly not unheard of (so no need to be too concerned). Migraines usually first present in peoples teens and early twenties. I would strongly recommend that you go see a neurologist or your PCP and have them check you out/clear you. Whenever a migraine presents itself for the first time (or the headache pattern changes) it needs to be investigated further. The probability of it being something more serious is very small, but you still need to be checked out to be on the safe side.
Best of luck!