Some questions on equipment and secondary classes

1) Are runes 1 time use only? Meaning if I use it on my current armor, would I need to find another rune in order to use it on my next set of armor? Or is it more of an item that is put into a "slot" that can be transfered to other equipment?

2) Is the zealous (sp?) bowstring a random drop, or can it be gained through some sort of quest at all?

3) Any ideas on the elite skill barrage (ranger) that anyone knows about would be greatly appreciated. I've heard of a mob that uses it, but apparently it isn't a boss. =(

4) When/how can a second profession be changed? Considering I can't get barrage, and don't have that many runes to level up my expertise attribute (which reduces energy), so I've found it a pain to use Judge's Insight atm. Thinking of switching out of monk to become a /nec or /mes. People expect heals and rez's as well, not to mention I'm one of the main targets if there are no primary monks.

Sorry for all the questions. Thanks in advance.