How to fix my 1991 ford explorer xlt?

i need help on how to replaced the lifter
how to do a tune up
how to do a oil change
how to fix my a/c since its blowing hot air
and how to fix my oxygen sensor… I know this is alot but i dont have that kind of money to fix my car. I dont know anything about cars. Please help im a mother of five and im doing this for them and my schooling to provide a better future for my family. Please help by putting step by step

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