Just bought this trunk lid online thinking it was in good shape. Unfortunately on inspecting the bottom I found this. Now, it's 22 years old so honestly I guess it's nto that bad. However it is going to be the most rusted out piece on my 21 year old car if I leave it like it is. How can I fix this without spending too much money? I'm not worried about the paint or having it perfectly smooth in the end, but I absolutely DO NOT want the rust to re-appear and start eating up the trunk or rear of my car.