I know you said "used", but if you're new to photography you might not know about Camera Mart. They're in Pontiac (on Telegraph Road). There's also Woodward Camera (in Birmingham -- but I think Camera mart has a better selection.) Those two stores are basically the last two "real" photography stores in the Detroit area. Camera mart will have quite a large selection of tripods set up on the floor. They do have a "used" department but I'm not sure if they deal with used tripods.
Also, a ball-head is generally the preferred type of head for still photos (e.g. landscapes). Release one knob and you can move the head any way you like. It's more versatile than a pan/tilt head.