1) the "M" denotes a modified movement. The 14060 and the 14060M are essentially twins. The 14060M has a movement that has been modified with a full balance bridge and larger balance wheel, calibre 3000 vs 3130, hence the "M" for modified.
2) not sure of the price though, but I expect them to be around the 15K mark. Maybe more...
3) there are two dial versions to the 14060M. A two liner which was pre COSC and a four liner which denotes COSC certification. Some purists says that the reason why they went for the 14060 was for the "clean" look. So the pre COSC two liner would be their choice. If you can find a 14060M two liner, that would be great.
4) classic sub, can't go wrong here. The only "pitfall" or gripe that I would have is the lack of a glide lock or easy link of a modern oyster bracelet.
5) easy...I would pick the 14060M 2 liner.
To the other sifus out there, please do correct me if the information provided is inadequate or incorrect.
Hope this helps
Cheers,
Patrick