A small heads-up. If your "everything is original" is a reference to the 110v wiring system aboard your Contessa, you may have little choice as to which current you choose. On my Contessa, the deck connectors are all 30 amp but the 30 year old wiring is dodgy at best and is not of a particularly heavy guage. I would not put more than 15 amps through it for fear of fire. Of course, if you are only running a laptop and a few lights it won't be an issue since you will never draw that much power.
I assume that you will be charged a higher rate for the 30 amp connection. Fifteen amperes is fine for what you have in mind and is even enough to boil a kettle.
And yes, replacement of the old wire is on my 'to do' list.