I bought a 3-pack for $24.00 at Verizon along with the case and dock. They had some kind of deal, if you bought 3 items you got a discount. It came out to be $30.00 cheaper with everything combined.
As far as the protectors go, it does take some practice but, after screwing up a few in the past on phones, I've gotten pretty good at it now. There is a certain way you have to do it. I usually use a credit card or something similar to push it on, rather than the cheap squeegee things that come with them.
I've heard pros and cons about them however, my buddy scratched his Mytouch 4G and, he wished he had put a protector on it sooner. He doesn't even know how it happened.