Caboose: right now, that ferret model is not set up for HL for the moment. Couldn't you do a mock up with a snark or head crab? You may ask chickenfist for pointers if needed, he has snarkibility in his new mod.
Tonight, i'll do a full run down with some friends and fellow designers on the topic. As well as properly lay out the work involved. You'll have all the info you need by the same time tommorrow.
As for me, I've been busy.
I'll do a few levels and try polish this off, the map the screenshot is incomplete.
I found a new way to filter the textures in photoshop that makes them look really clean, detailed, and contrasts perfectly in HL. Also, it makes the HL2 textures look a lot better. I guess valve fucked that one up. Here, take a look.
Unfiltered (unbaked, might look better with a bumpmap)
Filtered (baked, will look much better with a bumpmap but will also keep its contrast and tone. Proven to work as in the screenshot above.)