I would recommend that you look into the process yourself and decide IF you really need an attorney.. I believe that less than 1/2 use an attorney.. and the ones that do use an attorney take the same time and pay at least $1500... you can get a good start at the web site below and on the newsgroup alt.visa.us.marriage-based
I will say that if you have any out of the ordinary circumstances, you would be wise to consult an attorney, but if you do not, and you have a little time, it is often reasonable to do it yourself.. I did all of my own paperwork and it was a LOT easier than doing taxes...
You can also get an idea of how long the US part of the process is taking at your service center by looking here:
http://www.wkh.org/k-1visa/index.shtml
Hope you DON"T have to use the Texas Service Center (there are 4 INS service centers, the one you use is decided by your state of residence)
best of luck...
Derrick (currently processing a fiance visa with the Texas Service Center... day 111 of waiting, attorney would make no difference...)