Hey itt, I just bought a n800 and I have a few questions:
1) When I am not in wifi, and I want to use my blue tooth phone to connect to the internet, do I need to pay anything to my wireless provider(Verizon). Or is this completely free?

2) I know that I'll install tons of apps, and probably run out of the memory that is built in, so here's my question: Is making the flash boot from an SD card a dangerous idea and how difficult is it to do?

You could just use it as a pay-as-you-go, but charges are somewhere around $0.10 a KB. Unlimited data will probably be in the $40/mo range.

No, it's not free.

No, it's not dangerous at all and fairly straightforward to do (there are lots of good, very specific brain-dead guides and scripts available). A 512MB-1GB partition on your internal card to boot from will pretty much save you from ever having to worry about application install space.

(1) That depends on your deal with Verizon. Ask them.

(2) It's a pain sometimes for some people. In my opinion, it's not dangerous. If you want to avoid Red Pill (which Nokia considers dangerous), see Schmots's guide, referenced in Post #2 of the clone guide in my sig.

Well, Red Pill in and off itself isn't "dangerous", it simply opens up more options for people to get themselves into trouble by playing around. If you use it for what you need it for and turn it off once you're done, there's no real risk involved.

For the part where it says: "place card in card reader" can i just put the card in my n800, the put the n800 in the computer via USB then format?

On the other hand, there's no need to rush the change to boot from SD. The internal flash has much more room for applications than it may seem, because

a) The applications are usually much smaller than their desktop equivalents, one reason being they're normally stripped down (e.g. less documentation), and

b) The internal flash uses a compressed file system: If it looks like you have just 100MB left you can still install what looks like 100MB's worth of packages, but still have 50MB left.. I've lots of apps installed and I'm not even close to fill the internal flash.

So, if I were you I would hold back on moving to boot-from-SD until you see the need getting a bit more urgent. At that point you'll also have had some more time to get familiar with the device.