Any advice on buying my first professional Nikon?

I'm looking to spend between 700 and maybe up to about 1100. Has to be a Nikon, I already have all their lenses. I don't need to do video, only photos. I've been working as a wedding photographer, sometimes I need to blow things up kinda large, maybe at a max of 20" by 20". I've been looking at the d90 and d200 quite a bit. Also I don't mind buying a reasonably priced used camera if there's any especially good sites for it.

Definetly the D3100. I love it! I'm saving up for it now. I already have the D90 and the D5000 and the D3000 but i really want the D3100. You should definetly get it off of www.nikonusa.com

If you already have the lenses, how about waiting a tad more to stretch your budget to $1200 and get the Nikon D7000 body, which is the best nikon camera out in a long time.

if not, the D90 will fare well with what you want to do.

That kinda money is not going to buy anyhting pro level but it can buy something enthousiast amateur class. D300 would be my advice, same sensor as d90 but meters with Ai, better AF and much more robust.
If you want really pro level a somewhat banged up D2x or D2xs is possible but, honestly, the sensor difference between that and the D300/D90 is rather obvious.

So…
http://www.bhphotovideo.com/...amera.html
or
http://www.keh.com/camera/Nikon-Digital-Camera-Bodies/1/sku-DN029991024630?r=FE
or your local craigs list of course

If you're truly looking for a "professional" camera better have 4-times that budget.

Best ever Nikon Camera according to quality testing company (not just sponsored review sites by Nikon and there are many. D700 makes best sharp enlargements without much trouble.
expensive but hunt down secondhand.