1993 Ford Mustang HEATER

How or where should I look to fix the "heater"?

On cold morning cars defroster wont work, where should I look to fix?

Car does shakes a litle bit, what should I go check to fix?

My dash board lights work but certain section are dim, where or what should I look into to fix?

If you could please inform me with any information, to look into it and then take to a mechanic? Instead of always getting charged too much, I just want to address those issues. Not, what mechanics around my neighboorhood usually do.

Will be waiting for an answer, thank you so much.