Spiffy!

You could use a copper tube for a boiler. It would require some soldering and maybe some cutting/drilling for a flue or two. I'd also recomend a horizonatal boiler. I think that would prove to be more eficient.

Ease of building is more important than efficiency right now. Copper tubing is probably ideal, but I'm pretty sure there's fittings that can be used to fit stuff together without soldering.

I'm still not sure how best to do the boiler, I'm thinking something like this would be a good start:
http://www.kk.org/cooltools/archives/004782.php

Actually I think that might work better! XD
All you'd need to do is figure out how to get the steam from that kettle to the piston of your engine.

A tube would be worked into the lid of the kettle. Make sure you have some slack so it can be opened up, and you'll need a gasket on the lid to help seal it shut.

I figured that much. Although I don't have a lot of hands on experience with steam doesn't mean I don't know "How", perse.

When I was still in High School, for one of my tech classes, We had to build a boiler to use steam to turn a mini genorator and see how much power it would produce. I didn't know as much about boilers as I do now. I also failed that project because I soldered the steam nozel UNDER the water level of the boiler. *slams head on table*

Looking back and IF I had as much knoledge as I do now I would have utilized a steam dome and attach the steam nozel to it.