I want to add some features, such as wrinkles. I drew an image of some small details I'd like to add to him as a decal, but I can't make the white part go away? How do I get rid of it?
Without seeing an image of what you are seeing we are guessing here but...
There are generally two ways to get rid of the portion of a decal you don't want to see:
1. Use a Cookie Cutter decal (one of the options under the Decal Type) to make that area transparent
2. Use your image program (and/or A:M) to make the area you wish not to see transparent.
The first method deals with making a particular color transparent.
The second with creating a mask or Alpha channel to let programs know which area to set as transparent.
How can I make a proxy for my wolf?
The standard way is to make a copy of your model and then remove or delete portions that are not needed. WARNING: DO THIS WITH A COPY OF YOUR MODEL so you don't modify the original. Just open up the model and start removing what ever is not needed.
I should also point out that A:M does have an icon you can select to simplify the view of your model in a Chor window. In some cases, this may be all that you need.
It should go without saying that you should turn Particles off (Hair is a particle effect) as that will slow down your system's real time response dramatically.