Old newb stuck with a mission

For sure you need to get a better weapon. Max damage for a staff is 11-22. Make sure that if its a r11 fire magic staff for example, you set your fire magic to at least 11 or you won't do any damage.. Also, make sure it's modified correctly. Add an "insightful" staff head which can give up to 5 extra energy, and either a +30hp or quickening staff wrapping which can halve the casting time of your spells.

Is your armour from the crafters in Droknars Forge? That's the earliest point to get max level armour in Prophecies, however, a quick ferry ride from Lions Arch takes you to the Kaineng Center in Cantha where you can also get max armour.

Make sure you have the max armour possible for your character. And get it infused as soon as possible. Mursaat tear through non-infused armour in seconds. (Is it the ice cave mission that has the seer for armour infusion? It's been so long I can't remember). And make sure your armour is fully runed. It makes a huge difference.

Max As with everyone else in this thread, your advice is of course great, and I by no means want to be the argumentative !@$%#! here, but just thought I should clarify a point about base Weapon Damage (the 11-22 that he mentions). Unlike in GW2, the Weapon Damage from your weapons generally does not affect spell damage. For example, the elementalist skill Flare will do the same damage whether you're wielding a max damage staff, a minimum damage staff, a sword, axe, hammer, or even a tuna fish. This isn't true as much for attack skills (i.e., many Ranger bow attacks, warrior sword/hammer/axe, paragon spear attacks, and dervish scythe attacks), since they use the weapon itself to do the actual damage. You generally shouldn't be relying on the staff's Base Weapon Damage for your main damage, as except in the most particular of circumstances, 11-22 damage is pretty pathetic with such a low attack rate.
My point in bringing this up is that, say you find an excellent air magic staff with otherwise perfect* modifiers, but a rather useless requirement of 11 air magic. You can still use the staff without wasting 11 points in Air Magic (a skill line not particularly useful to a Necro primary), and all of the modifiers will give their full effects.

I'd recommend going to Kaineng as Max said, since that armor is relatively cheap (6k or so for the whole set, I believe).

*"perfect" being defined here as "whatever you really want at the time".

As with everyone else in this thread, your advice is of course great, and I by no means want to be the argumentative !@$%#! here, but just thought I should clarify a point about base Weapon Damage (the 11-22 that he mentions). Unlike in GW2, the Weapon Damage from your weapons generally does not affect spell damage. For example, the elementalist skill Flare will do the same damage whether you're wielding a max damage staff, a minimum damage staff, a sword, axe, hammer, or even a tuna fish. This isn't true as much for attack skills (i.e., many Ranger bow attacks, warrior sword/hammer/axe, paragon spear attacks, and dervish scythe attacks), since they use the weapon itself to do the actual damage. You generally shouldn't be relying on the staff's Base Weapon Damage for your main damage, as except in the most particular of circumstances, 11-22 damage is pretty pathetic with such a low attack rate.
My point in bringing this up is that, say you find an excellent air magic staff with otherwise perfect* modifiers, but a rather useless requirement of 11 air magic. You can still use the staff without wasting 11 points in Air Magic (a skill line not particularly useful to a Necro primary), and all of the modifiers will give their full effects.

I'd recommend going to Kaineng as Max said, since that armor is relatively cheap (6k or so for the whole set, I believe).

*"perfect" being defined here as "whatever you really want at the time".
He's right of course. 11-22 damage is negligible compared to the damage your spells can do. And your henchmen. Its all about how you set your skill attributes. Spiteful Spirit can do lots of damage for example, but only if you set the attributes high. Having a r9 weapon frees up attributes cos you only need 9 for it to work to is best. With runes, you could set the attribute to 6, the other 3 coming from a superior attribute rune, to give 9.

Now you're starting to get int the mechanics of the game. When you're at the elite areas, a single attribute point in the wrong place can make a huge difference.

And never, EVER underestimate the damage a tuna fish can do.

Max.