Well, most part is relatively easy. In what program do you want to edit? In general you can say that if a line ends in a lower case letter or starts with a lower case letter, than the paragraph break is incorrect (not always true, but almost always). You can do that with a RegEx. The correct syntax really depends on the source document and the editing program.
If a new paragraph always starts with an indent, I think I can think of a S&R command to solve the remainder of the lines. Again, not a 100% garantuee, really depending on the programs you use.
If you tell us which program you use, we might be able to help you.