I am relatively new to reloading as well, so I don't want to pose as some sort of expert. But, I would encourage you to get your hands on a copy of "The ABCs of Reloading." You can pick it up on Amazon for $17 or possibly check it out from your local library for free as I did. It is not a load data manual, but a good overall treatise on reloading. From there I would pick up one or more loading manuals such as Lyman's 49th edition. Do this before you load your first round. The temptation is strong to jump right in, but don't underestimate the danger to yourself and others from doing so.
Get a kinetic bullet puller and pull the 20 mystery loads. You can re-use the bullets and brass, dump the powder. Do a search for how to decap live primers.
Good luck and be safe.