i wouldnt reccommend buying fpga board if you only want to mine bitcoins but if you want to learn fpga development i guess you would already know what you want
also pretty decent programming skills and good understanding of electronics are a prequisite
You almost nailed it. I have the coding skills and I do a lot of embedded development, mostly with PICs but also H8 and the like. I never used FPGAs before and I've been waiting for an excuse for a long time now, so bitcoins might very well be it.
I have a pretty simple understanding of electronics, but I do have people

So if I had to jump out of a dev board I could, and in fact would have all the expertise and industrial equipment available to me to do a full hardware implementation from scratch, but that obviously comes with an extra cost.
So, yeah, I *should* already know the answer to these questions if I had done my homework, but it's hard to keep up with everything and the bitcoin community has been the most helpful I've ever met... ever!