diffuzion wrote:
it started to leak again

I am not sure what to do here. Should I just go to a dealership and trade in my old vespa for a new one or try to get a new cylinder head and valve head?
You have a few options here. Unfortunately some will require a head removal.
1. Disconnect the shocks and air filter
lift the bike up a bit, enough to Pull the valve cover off, and check the torque on the head. Retorque if necessary.
2. Pull the motor, Call Scooterwest or Scooterparts,co, get the thicker gasket and install. This could help with the imperfection of the new head.
3. Call Scooterwest or Scooterparts,co, they would have some Verified good used heads on the shelf, for about $300 dollars or so.
Order the gasket kit and stud bolts, along with the O'rings.
Unfortunately I think these are your best solutions.
Good Luck, sorry to hear about the trouble.