Need advice on how to save on repairs

I have a 2006 Grand Marquis with 113,000 miles on it. I am a recently divorced woman on a very limited income. Recently my now ex-boyfriend paid to have my alternator replaced. If he hadn't done that I would not have had the money. I am worried something like that or even more expensive could happen. I would appreciate any advice on how to save on repairs or what someone would do in my situation.