I am considering signing a commercial lease for retail space. Provided the landlord and I fully agree with all the terms should I still have it reviewed by an attorney? How much would this run approximately?

Well, you don't absolutely have to have it reviewed by an attorney, as long as you're willing to lose every penny you invest, plus maybe all of your personal funds as well.

Seriously... my form commercial retail lease is 40 single-spaced legal pages. Do you think there might be something in there that is not to the other party's advantage?

Speak to a few attorneys. Some may charge $500, some may charge $2000. Whatever you end up paying I don't think you'll regret it when you see the things they come up with that could be harmful to your position.