Hey Dave, here are a few answers to your questions.
1. The guitar isn't particularly collectable since every Japanese company at the time produced a 335 copy. I'd place current value around $300 USD so you got a good deal, but don't expect exponential growth.
2. You can determine the exact date from the serial number. You guitar was produced in 1972. If you want to know the basis of my conclusion click here:
3. The Arias are nice instruments, but they are not Gibsons. The main issues are the tuners, pickups, wood and construction quality.
4. I think Arias are a nice guitar for the price. You got a great deal. Enjoy it.