Part of used car ownership is assuming the previous owner never changed any fluids or did the plugs/wires or scheduled maintenance unless there is a receipt for it and even then. I ALWAYS suggest doing oil, trans fluid, brake fluid, differential fluid and inspecting the brakes. I'd also do the spark plugs.
Also if you take it to get it done do NOT get it "power flushed" or whatever. Just a full drain/fill of the trans and converter.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.