It will be expensive to do so. First, you have to prepare the return *EXACTLY* as filed, and you will pay for that. Then you have to make the program *think* you filed your tax return, and *think* it was processed by the IRS. Then, and only then can you complete the amended return. Amended returns can not be e-filed. The IRS says so. You have to print, sign and mail it to the IRS. So if you have just one teeny-tiny mistake on the original return, when the IRS receives the amended return you may find yourself in a tax hell nightmare from which you will never awaken.
If you believe your preparer did it wrong, then gather your facts and present them to your preparer. If they did "in fact" do things wrong, then since you paid them already they would be obligated to "make it right" at no additional charge to you. (Unless it's because you did not provide them necessary information from the start.)