Is there anything else wrong with the door? Rollers can be fixed/serviced quite easily in many cases. As to your question about a 4' French door, I would be cautious about that. French doors are notoriously sensitive to operation and size. A 4' door, hanging out in space, hinged, and heavy (i.e. full glass) is a recipe for operational difficulty in my opinion. There are plenty of sliders that can be opened with a single finger's effort. I think you need to see one of those type doors and feel the operation on it to make and apt comparison and then decision.

I agree with Fori, you are talking to the wrong sales people. For years early in my career, seems almost all I did was change out sliders to french doors. For your opening size and situation, you could use several combinations of door and sidelight combos. For example, a pair of 32" swinging french, with a 32" fixed sidelight. If your rough opening won't accept that, perhaps a 30" sidelight and/or 30" doors.

You need the pros for this because you probably need a whole new insert. There is an inert gas between the two glass panels and when that is breached a whole new panel has to be ordered pre-made and replaced in door. I would call a window source that carries the brand you have. They can help you order new one and install it properly. Good luck. So sorry for your troubles. Insurance might cover if all your damages exceed your deductible.

mirror and frosted mirror are more economical than most clear or frosted glass. But the cost difference is small enough that when they go on sale at big box store, it easily swaps or evens out. Tinted mirror is expensive as they are not as popular.