Hi,
We have a sample training lab available on our blog, and one of them talks precisely about an event planner form.
One of these free training labs is: here and here.
The second sample training is here: part 1, 2, 3 and 4.
It sounds like your scenario is pretty detailed, so I doubt that you will find one step-by-step guide for your specific scenario, but hopefully the labs above get you started with InfoPath. Hope these help!
If you would like InfoPath training, click here, and if you would like consulting services (where an InfoPath expert designs the solution for you) click here. Self learning is very rewarding, but also time consuming, so if you need the solution ASAP, then more individualized help might be a good idea.