I hope that Marcus Daniels <marcusd@cathcart.sysc.pdx.edu>, the fellow
who did the last NT port can answer the questions I can't, but:
I would recommend basing your port on Guile 1.2, or a nightly
snapshot. It's six of one, a half dozen of the other: there have been
bugs fixed since the 1.2 release, but probably new ones introduced.
Guile 1.2 is ftp://prep.ai.mit.edu/pub/gnu/guile-1.2.tar.gz.
The snapshots are ftp://ftp.red-bean.com/pub/guile/guile-core-snap.tar.gz.
I can't comment on which compilers folks have used, nor on the
difficulties of porting it to VC++. In the end, I suspect you, or the
person you hire, will be the authority on such things.