I was wondering if I could be sued for using a logo of a company that used to be well known, but is now backrupt...has been for over 10 years?

Rights in trademarks can be transferred in bankruptcy. While nonuse of a trademark can mean the trademark is abandoned, there are cases where trademarks have been transferred and used by a successor to the bankrupt business, or just the part of the bankrupt business that used that trademark. This is because there was no intent to abandon the trademark. Clearing rights of intellectual property of a bankrupt company can be tricky for this very reason - often it is not clear from the record how these rights were disposed and whether there is another owner.Slightly altering a trademark does not necessarily make it nonfringing. The question is whether the trademarks are confusingly similar, which depends on the similarity of the trademarks; whether the trademarks are being used on similar goods or services; whether the goods or services are offered to similar customers through similar marketing channels; and whether there is any actual confusion among consumers. Sometimes identical trademarks are not infringing, and sometimes trademarks that are not identical ARE infringing. You have to look at the whole picture.