I was invited to join a DFRPG campaign, but I don't have any RPG experience.

The DM knows the story universe pretty well, but none of the other players do.  They're all seasoned RPG folks, though.  I've read each book at least three times, so I figure my knowledge of the Dresdenverse will compensate for my noobness.

So I'm an apprentice wizard with 4+ lore, and one of my jobs will be to advise the other players on magic and politics.  I figure I'll learn the game as I go.  For now I'm just interested in figuring out some fun spells, and I'd like your advice.  Also, if you have any examples of standards, I'd be interested in hearing them.

Anyway, I've decided to go earth/water mage, and there isn't a whole lot of text support for those two elements.

Leg crusher:  A disabling spell that opens a sinkhole below an opponent and quickly snaps back, crushing leg bones.

Feasible?  I'm worried that the DM might accidentally make me kill someone by opening the hole too big and crushing a torso or something like that.  Is this something I should be wary of?

Coinshot:  This is stolen from Mistborn.  Harry uses his sword cane as a focus for spells involving magnetism.  Are there special rules governing this?  Do magnetic spells always attract metal towards the caster, or can I be more versatile with it?  For example, can I take a handful of ball bearings and shoot them outward towards a hostile?

If not, magnetism still has the advantage of disarming opponents and maybe I can even hit people with metal objects when my opponent is between me and the object itself.

Dampening Feild:  Can I use water to dampen the magic of others?  Say, pull ground water out of the earth and interpose it between me and an oncoming evocation?  Can my earth magic help me pressurize the ground water to assist pulling it out of the soil?

All of these ideas are pretty high-octane.  Would they cause me an unreasonable amount of stress?

These are just my first ideas, I'm going to mull t over some more.

Thanks in advance

I'm sure this happens all the time..  I came up with what I thought was an original idea, but somebody had beat me to it.  Nothing is new under the sun, and all that jazz.

I'll probably never get around to writing it, but I had an idea for a novel that blended contemporary urban fantasy with sword and horse through the simple expedient of introducing something I've been calling "the Shadow".  It came upon humanity as a surprise, and nobody (it seems) really know what caused it, why it happened, or how to reverse it.

The Shadow is some substance that had flooded the earth that caused a complete arrest of not only technology, radio waves, electricity, etc... but also combustion itself (happily taking guns out of the equation, as well).  This is just a plot device, though.  The world-building, the characters, and the messages would all be my own.

The problem is that the idea isn't so original.  The show "Revolution" is using the same idea, but I've been told that an author named S.M. Sterling had published a novel using that very same idea in 2004.  I haven't read it, and I don't want to for fear of it having an influence over me if and when I do decide to write this thing.

Which leads me to my question:  If I did write a novel using this idea as a major plot device, and I put my own spin on things to make it a unique story, would I then be able to submit it to agents without those agents rejecting it outright because of a "stolen" idea?  I've read enough Butcher to understand that borrowing ideas is part of the craft... *cough*Pokemon*cough*...  but this seems to me to be more significant than that. 

I don't know why I'm worrying about it.  I'll probably never get around to it, and even if I do finish it, I don't really stand a chance at getting published.  I have about /zero/ fiction writing experience.  If I do this, it'll just be something that I do for myself (and maybe I can force it upon a few of my closer friends).  I have free time, I'm leaning towards getting serious about time management and actually giving this a serious go..

Thoughts?

At the bottom of the index page where online users are listed, does everybody see their own name listed first, or am I just special?

I need to improve my grammar skills.  I can devote some time to this over the next three months or so.  I'm not really interested in taking a class.  If I pick up a textbook and workshop on my own, I think I can manage.  Is that a good idea?  If so, what book(s) should I use?