the campaign isnt really an epic campaign, its just become that since we're nearing the final stretched where it gets reaaaaly nasty.
Also, not all plot quests are nasty, but a lot are recently so be warned.
I think Talan was level 9 or 10 when he went on his first plot quest (which was also my first plot quest.) It was and impromptu thing where L shouted "doing an impromptu quest in... oh 10 minutes, meet at X" and I happened to be on at the time.
And really, unless its a really nasty quest with a strict party limit (since every 10 ms of lag adds +1 to the CR of an encounter hehe) come anyway. If you are making a fun (or helpful) RP contribution NO ONE will challenge the fact that you are level 7 and everyone else is 18+.
On many quests theres a period (30 min, sometimes longer) at the begining where we discuss whats going on, any new information that has surfaced thats pertinent. Even if the quest is dangerous anyone can come to the begining (i think) and participate and listen to the exchange. However, if you dont know whats going on being there will likely be a frusterating experience.
The only advice I have on that is, do some research first. Find out the background of whats going on. If you interrupt and ask a smart question, most likely someone will stop to answer it, but its hard to know whats a smart question if you dont know the background.
Also it would be helpfull to meet someone before the start and make friends, then stand next to them and whisper your questions, its not that people hate you or dont want to answer questions about the background, its that they dont want to interrupt the main flow.
so yeah... just call me "Wild Tangent" becuase... well, I always seem to go off on one. But, the stuff about questions and info chats before quests is pretty much a good idea for lots of quests.
Forgot what I was originally writing about...
Oh yeah, its possible to get involved in the plot even if you arent capable of surviving some of the more combat oriented plot quests.
Bris is running something soonish thats plot related, not sure of the level req though.
::End Rambling::
-Wild Tangent
PS - the main plot has more subplots than I can even count, I kid you not.