I'd think that the cost from Omega will depend on what they decide needs to be replaced. The crystal and crown are obvious. The bezel may be OK and just needs a cleaning. My guess is that they will replace the handset. The dial is a bit scruffy, but I imagine they would leave that alone. The bracelet needs some tightening around the end links, but it's an 1171/633, which is pretty solid and durable.
As for the movement, it's anyone's guess what's going on, although the lack of a stem is a good reason for it to be a non-runner. It may be OK with service, or maybe not if there is actual internal damage. Fortunately, these things are fairly robust. That said, if you want to have a bit more control over what gets replaced and at what cost, you may want to consider using an independent watchmaker with an Omega parts account.
Bottom line? I think it's a crap shoot, but not out of the question you could be in business for $3.6k or thereabouts. That's certainly on the lower end of the price range for a serviced, wearable Speedmaster; there have been some decent eBay sales in the $3,500 range recently, albeit not with any sort of service history. Personally, I would probably have held out for a better example, but that's just me.
(BTW, you really should've created a new thread for this)
