We don't have a published price list to quote here, and giving you a made-up number would do you no favors. What we can tell you is what drives the cost on a job like this: door material and insulation rating, whether the opening needs framing or track rework to take the new door, and whether the old spring and hardware can carry over or need full replacement.
Old Greenwich's median household income runs well above the wider service area's - $250,001 against the broader area's $183,112 - and we see that reflected in the doors people choose here: more insulated steel, more custom wood-overlay panels, fewer base-builder doors. None of that changes the install process, but it does change the number on the invoice. We'll walk the opening, quote the actual door and the actual hardware work it needs, and you decide from there.