If you've never done rooting/flashing before, an Amazon device is not a good place to start. I did it on a HDX 7 only after a ton of reading, and the consensus is that it's easy to get it wrong and brick the device. There are no escape hatches like there are on the Google Nexus devices. I've done this a ton on my Nexus 5 and my HD2 several years prior.
Also note that the HD 6 and HD 7 are still not flashable, and they've been out for some time. Amazon seems to have gone out of their way to make this a difficult device to tinker on.
My recommendation is to find a well-treated used Nexus 7 and you will have a much better time of things. They are much easier to flash with better ROM support. Please don't buy this thing with the expectation of enjoying some weekend tinkering - it's not worth your time.
(I suppose I'll caveat that the one scenario where it would make sense to get it now would be that v1 firmwares contain bugs that will make your life easier when exploits are found, but still - probably not worth it)