What is the estimate on replacing an engine on a 2001 Mazda Protégé?

What is your question?

I was told that I need a new engine for a 2001 Mazda Protégé DX 4DR Sedan. The engine is a 1.6L L4 DOHC 16V engine. I was told originally that I needed to replace the timing belt when I explained what happened to the car (that it would not start, etc., see below). The mechanic told me that the head gaskets needed to be evaluated to determine if they were "burned up" as a result of the overheated engine. My original problem was that the engine overheated (smoking profusely) on the highway. I got a tow home from AAA. When I later went to start the car, it did not start (not even a sound). So I took it to a local mechanic who explained what the repairs would likely involved based upon my description of what happened (see above). I would like to obtain an estimate of what it would cost to replace the entire engine, e.g., cost of a new engine (used) and labor costs. Thank you.

What makes this problem better or worse?

Not applicable. Engine does not make a sound when I try to start it.

How long has your 2001 Mazda Protege had this problem?

The car has been sitting in my drive way for about two months.