cost major problems and upkeep for diamonn

What is your question?

diamonn is 18 yrs old her odometer is 179,146, she,s had 6 prior owners,based on autochecks history report ,never been in a accident,i.ve had her for bout 3 months,her engine light just came on,and the driverside window stop workin along with heater, since I,m not sure how she was beeni takeing care of,other then those issues,where should I start,to insure proper upkeep