It is awsome to hear that people are actually trying this! Paul Stamtes actually won a competition in petrolium poluted soil cleanup. So it works. Here is what i think you have to do: On Paul's website, you should be able to purchase a mushroom cultivation kit. Make sure it is oyster mushrooms since that was what he used. the kit will come with a spore seringe, a plastic bag and probably some kind of substrate. Im sure it also comes with instructions on how to do it. Also, depending on the size of the polluted patch in your yard, you may want to get a couple of these kits. they wont be more than $20 each. cultivate the bags of substrate just like it says (keep everything vary sterle or it will grow mold) after 2 weeks of so, introduce the mycilium (cultivated spores) into the soil. This is called casing, you may want to do some additional research on it. break up the mycilium underneath a 1/2 to 1 in. layer of soil. water the area and cover with a tarp for another 2 weeks. when the tarp is uncovered, if there are not mushrooms, there will be soon and not only should the petrolium be broken down but you will have a nice crop of mushrooms! Actually, you probably shouldn't eat them even though paul stamets tested his mushrooms cultivated this way and they contained no hamfull chemicals.