have you ever used google sketchup? It's very simple to use and it's free. I wouldn't bother with buying plans or instructions. Draw out what you want so you have dimensions then fram the shape you want with 2x4's. You can buy the paneling of your choice to "skin" it and your good to go.
I've built one bar this way, and have plans to build a second at the permanent camp site we'll be putting our camper on shortly. There some pics of how I built mine in the link in my sig.
I'm actually the friend in question. The internet failed me in providing any kind of free DIY instructions, so I'm thinking of just winging it like Gfei suggested. But if anyone has another 2 cents to throw in, please do!