I'm a level 7 Necromancer/Elementalist, I was wondering if there are any "dungeons" or raiding areas in Guild Wars? Also, PvP is really confusing for me. I don't know how to enter it on a RPG player.

There isn't really any dungeons or raid areas in Guild Wars. Look to WoW for that.
PvP - For your person, there is the ascalon arena if you're on the Prophecies campaign... look for a NPC in Ascalon City for it. (Can't remember name.) If you're looking for the real PvP action, you have to make it through the main game until you reach either Lion's Arch in Prophecies, Kamadan in Elona, or Kaineng Center in Cantha. From there you can go to Temple of Balthazar, which is on the PvP Isle.

depending on where you are on your character? prophecies, factions, or nightfall? and there aren't really dungeons or anything, although there are cooperative missions that you can access with in the game [various missions requiring alot of planning] and people will hate you if you enter PvP with a level 7 character. unless you're gonna enter with a RP [roleplaying] character it should be level 20. hmmmm there is random arenas, team arenas, alliance battles, heroe arenas, etc. send me a message if you need help.

First time PvPers will definitely find PvPing a little confusing. One thing is for sure however, is eliminate the opposing team. Which method you use is another different matter.

As a Necromancer, your role would be to disrupt physical attackers. Or even spellcasters, depending on how you make your necro. You may need corpses for some of the skills, and that isn't really dependable in PVP, especially the RAs. If i'm not wrong there're hardly any corpses and when you die your minions run amok. 'Wells' are another story, you can use them to your advantage always.

Remember, play your proper role in a team in PVP. Don't let your team mates down and they won't let you down. Unless it's in Aspenwood and there's friggin' leeches everywhere.