Congratulations on being chosen in the DV lottery!
There is really no way to answer this here; many things will impact the answer, and the things you mention really aren't the things that have the biggest impact.
For one thing, it appears you are here and in valid status - we can assume you want to process here in the U.S., but we don't know for sure. I can tell you that while I don't charge people processing through consulate abroad anything additional over what I charge people processing here, some attorneys do as this process often involves more work, and dealing with certain consulates can be very difficult to deal with.
If there is any issue with your case - some potential ground for exclusion - your case will be more difficult and involve additional fees. No way to determine this without interviewing you concerning your background (and even this won't catch something like a health-related ground that would appear during a medical exam)
Finally, a more experienced attorney may simply charge more than an inexperienced one.
All I can suggest is that you research qualified attorneys, contact them to discusss your case, and get fee quotes..
In addition to the information in the previous response, note that some immigration law firms do not charge a fee for an initial consultation, and that often is a valuable way to have your situation assessed and a fee proposed for you to consider.
[Note: Consistent with Avvo policy, this communication is intended as general information and not specific legal advice, and this communication does not create an attorney-client relationship.]
David N. Soloway
Frazier, Soloway & Poorak, P.C.
1800 Century Place, Suite 100
Atlanta, Georgia 30345 www.fspklaw.com
404-320-7000 * 1-877-232-5352 * email@example.com