I wonder why you want to solve this case on your own ! Since large amount of money is involved and you want to solve it on your own, seems like there is some fishy going on ! Is that money legal ? Is there anything else you should be afraid of authority besides you are out of status?
If you are really that innocent, then look for some immigration community or something similar organization working for legal / illegal immigrants for their rights. If you can post it to sajha, you should be able to at least search for such organization in internet. Being illegal does not mean you are deprived of every aspects of human rights.