We have our taxes done by a big firm. Both personal and corp taxes (but we are a small corp).
You will likely find chrages of anywhere between $30/hr to $150/hr, or more.
Checking references is always a good idea, but I got a dud even after checking refs. Most offer a free 1-time consultation through the Chamber of Commerce. Use that to talk to them, see which ones explain things thoroughly to you, so that it makes sense to you.
We handle all our own payroll and monthly and quarterly filings, and the simple annual filings (SS, FUTA, SUTA, and all the others that quickbooks can do for you with a few clicks of the mouse), but we use them for annual returns we can't (which will differe from yours as a partenrship). we get charged about $500-600 annually, and they only work with us for 1 mo out of the year.
One thing you'll have to be aware of: Because this will be the start of your CPA relationship, you will incur quite a bit in hourly charges just so they can familiarize themselves with your business. They need to look at past records, look at the current year's stuff, etc. One thing that'll help keep charges down - have everything organized. If you use quickbooks or some other software, have that up to date when you see them. It'll save them time, and you $$.