Assuming you do have copyright ... You should obtain consents from the subjects of your video. Unless you're dealing with producers, investors or distributors, you can probably get by with a videotaped consent. Tell your subject that you need their consent for the following uses (list all your anticipated uses such as distributing DVDs, posting on the web), and explain that you may not use the interview in its entirety-- that is, you may use edited segments. Make sure that there is a real consent -- even something as simple as "Yes, that's okay with me," will work. Then save that video. As we mentioned, if you're dealing with money people or distributors, a written consent -- with its additional provisions and releases, for example, permission to use the priest's name and image in advertising -- may be preferred.
Books that can help. You can find the forms you need in Getting Permission: How to License & Clear Copyrighted Materials Online & Off (insert FTC disclaimer) and in Clearance and Copyright: Everything You Need to Know for Film and Television (a great primer on permissions for film makers).
Can't afford a lawyer? You may not need much money to get legal advice. Chicago is one of several cities with "lawyers for the arts" services. This may include pro bono advice or other low cost services. The Dear Rich Staff used to provide free legal advice at the CLA office in San Francisco but then we created this blog, instead! (Speaking of religion, the staff is currently digging this book)