T5 Polini 152 Kit stupid question

.. but do i need a head gasket for the Polini 152 kit? It comes with a base gasket but no head. Does it need any sealant or anything. I know its probably an idiot question but i'm a bit new to all this!

I bought my T5 classic with a Polini kit 18 months ago. After a week of running the bike, it seized! the rings were inbedded in the piston. The autolube has been switched off and i had been using the plastic measuring cup for the 2 stroke oil. Every fill up i added the amount of oil the cup showed me (and made sure it was mixed).. but i guess i didn't add enough! I had been informed that all other necessary adjustments had been made to the engine etc.

I bought a new 152 kit, despite toying with the idea of buying a new stock kit and just turning the autolube back on, and only just got around to fitting it. Whilst taking everything to pieces i also noticed a hole in the exhaust and have bought a standard type sito as a replacement (it had a sports exhaust before)  

I've been riding various bikes for the last 16 years.. but a bit of a numbskull when it comes to geared Vespas. Any help would be great!