[silasdb]

Others have said that, but I'd like to put emphasis on getting everything in source control. If other developers don't know about source control (!) they will love it. I'd spawn my own local source control solution for my own control and after a few changes, show them the advantages.

Second: making a change without tests is like walking in the dark without a flashlight. Having tests is a very important thing.

Read Working Effectively With Legacy Code", by "Michael Feathers, one of the best books I've read that really can help in situations like that. In summary, it boils down to having tests to aid your changes you need to make.