Greetings Anoose, I have a month on you; the tpad is my first WebOS thing. Here are some answers that I've found that should help:
1) follow the directions at the link here for PreWare:
alternatively, in the app catalogue, buy the Preware documentation and it will cover the same material and then some. Installing Preware will enable you access to patches and utilities that you'll find to be of interest.
to get into dev mode you can do the updownupdown thingy or (my preference) use "webos20090606". It's shorter and easier to remember. There's also a homebrew app that'll do it automagically. Woot!
2) Within Preware, the current version of Uberkernel (must also have Govnah installed) will overclock to 1.5 GHz. The 1.7 GHz kernels are the test ones, so to play with those, you would need to consider whether or not you're ready to be an alpha tester
3) I have no idea; not having either one, nor desiring either. My understanding is that it's not really necessary if you've got Preware and the associated capabilities
4) If you have a Pre phone of some sort, or actually an Android, and want to be mobile, take a look at the Preware freetether app, as well as Private browser (in the app catalogue), Overlord monitoring, etc...
spend some time in lurking in the Homebrew forums.
Get a good bluetooth headset if you plan to use Skype with the tpad.
Let the kids play with it; it's interesting to watch how fast they pick up working with WebOS, and then show you new things.
5) my personal favorite way to close things is to hit the center/home button to turn it into a card, then pull the card down and let it shoot up to the top, whilst it makes Angry Bird sounds. Cracks the kids up; cracks me up. I'm a silly guy.
Overall, have fun with it! I like it better than the droidthings I played with, and iOS isn't personally intuitive to me