Vacating Tenant

Our grandfather gave a small portion of his house as a shop on rent in the 1990s. Our grandfather expired in 1990s and the tenant also expired in the same decade. Subsequently his son took over the shop and used to run his small business till 2007. Since 2007, no rent has been paid by them and they have kept the shop under lock and refuse to vacate. The rent paid was a meagre Rs. 150 per month at that time. Further, our grandfather did not leave any will, thus my father and his three brothers are legal heirs. As per our elder uncles, there was no formal/legal agreement between our grandfather and the original tenant. As per the original tenant's son, his father gave a sum as a pagri to our grandfather. He claims that he has pagri papers, but we believe that they are fake. The current situation is that we do not wish to file a case in court because we cannot afford the legal consultation fees. So, I have the following questions: 1. Can we register a case of trespas against the tenant? 2. If we forcefully break the lock and take the shop (which is a part of our house) into our possession, what are the probably legal repercussions? 3. What other alternatives are there apart from registering a case against the tenant and getting vacation notice from the court?