Is copying and pasting information from the internet into a research paper, with sources cited, without modification except for minor changes, considered cheating? And what should I do if it is?

There are two issues here: First: Quoting and transmitting are permissible if accuracy and academic honesty are observed by attributing the effort to its owner, stating its source, and clarifying any additions or modifications.

Second: Copying an entire research paper from the Internet is not problematic if it is requested by the professor or if he does not object to it. Otherwise, it may be a form of cheating, especially if the requirement is to demonstrate the ability to gather and refine information in the student's own style.