I am just beginning to familiarize myself with the gear involved in successful FPV set-ups, so I'm not qualified to answer many questions about it. But from what I understand, and you more than likely do as well, you will still need a video monitor, and power supply.
As for the gear, there have been reviews that state the cheaper version of the same camera (non 420TVL), is just as good, if not better. Also if you live in North America, you may have less compatibility issues with a NTSC camera.
I think the rest depends on your radio system, if you have a 2.4 Tx (as I do), then 900MHZ should be fine for video. As for the 100mW, I think 200mW is the lowest most folks recommend, I am not really clear on this area yet though, so hopefully someone will enlighten us here.
I just bought that 900MHz 200mW. I was going to pull the plug on a $300 ReadyMadeRC system but I thought it would be better to try it out for $50 first. RCModelReviews' video is what made me go ahead and get this from HK. It can be upgraded with better antennas and stuff as I progress.
I honestly think my 5.8Ghz system will do much better than what Bruce from RCReview was using in that video. I get a lot less interference all the way through my video. Having said that, I've only flow out now 500meter but there was no difference in the quality to this: