The forms are not that difficult. That's why many people complete the forms themselves. The first form is I-130 for the Visa Petition. There are extensive instructions to this form. Second, you need a priority date that becomes current. Third, file an application for permanent residence or a green card. Fourth, enter the U.S. with an Immigrant Visa.
Do I need a Lawyer?
Although many people don't need a lawyer for this process, there's nothing wrong with asking for help. In fact, if you need help, get it. You don't want to make a mistake with such an important process.
You want a lawyer that specializes in Immigration Law. Finding a lawyer on AVVO is a good start. Asking friends or family members that have gone through this process with a lawyer is also a good idea. Nonprofit organizations can also help you find a good lawyer.
Be careful if a lawyer walks up to you in USCIS office and solicits business. Also, just because a lawyer dresses well and has a nice office doesn't mean the lawyer is any good.
I do not practice Immigration Law, but can refer a few good lawyers.
Pros and Cons
Pros: Work experience or education does not matter.
Your spouse and unmarried children under 21 years of age generally qualify as derivative, accompanying relatives.
Cons: It can be taken away if you live outside of the U.S. for too long, commit a crime or fail to notify the government of an address change.