Modern Vespa

Hi people
What I'm after is I've bought a 150 kit and I'm going to be fitting it my self what it is do I need to upjet main jet when I'm going to a 150 if so what jet would I put in and do I need to remove the valves to put the piston in or is it all plug and play

You don't need to change the jet. Or remove the valves. But you do need to remove the engine from the scooter and remove the head from the engine. Unless you can do that, find someone to help you.