I took the battery in to autozone to check it since its under warranty and they gave it a deep cycle charge. Car started first time i cranked it. I let it run for a bit but i had to give gas sometimes when it sputtered. The brakes aren't really working. The discs are rusty and the red parking brake light stays on. Other than that though it runs like it always has. Any diagnosis?
thanks

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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.