You won't find wools with a good deal of lanolin in your LYS because it's mostly removed for processing, particularly for dyeing. But, you can relanolinize them easily. (I just got some gorgeous natural, handspun wool with tons of lanolin from an MDC mama in Finland. The lanolin made my hands *so soft* just while winding the hank into a center-pull ball
) Lanolin will also improve the feel of the wool, helping reduce it's scratchiness. Lanolin is only one aspect of wool's waterproof-ness, though - the important thing is the structure of the fiber, and that isn't affected by the processing. So, don't worry about how much lanolin is in it at time of purchase.
You will get the best results from 100% wool, and very good results from a blend of wool and another animal fiber (i.e. mohair or alpaca) which may actually have a nicer feel to them. I have no confidence in a blend with any synthetic, and a blend with a very absorbant plant fiber (cotton, linen, hemp, ramie) is a recipe for disaster. Again, it has to do with the structure of the wool. Wool does not wick moisture easily, but it does breathe easily. Have you ever looked at a piece of hair under a microscope? It's all scaly. Wool is like that, but even scalier. Those scales stand up from the fiber like this:
\ \ \ \ \ \
------------------
/ / / / /
All running in one direction. When two of those fibers come together, the scales lock into one another. Thus, they hold on to one another (and to all other fibers locking on to either of them.) There is plenty of airspace to let air evaporate, but none of it contiguous enough to actually wick via capillary action very well. Lanolin helps reduce wicking even further by greasing up and kind of plugging some of those airspaces... but if you saturate it enough, it will diminish the breathability of the fabric.
As for kinds of wool, I guess you mean weight. Personally, I wouldn't use anything lighter than worsted - even if the yarn isn't wicking moisture, if the fabric is very thin, you can force water (urine) through it. I wouldn't go as heavy as a bulky wool, unless you're making a really thick one for nighttime use. "Traditional" worsted weight yarn is specified as 220 yards per 100 grams, 5.5 stitches per inch. But, there is some slight variation there - you can get heavier worsteds.
For the wool pants, it depends on how heavy you want them. Brown Sheep makes a nice wool/mohair blend (85/15 I think) that is really soft. But, it's a really dense heavy worsted. If you want something a bit lighter, Cascade makes several different wools in perfect worsted weight and alot of gorgeous shades. Their basic line is Cascade 220, they also have a gorgeous wool/alpaca blend. You can get Brown Sheep at Ewe and I in Bryn Mawr (I didn't like the attitude of the folks at that place, though,) or up in Bethlehem (I can't remember the name of the store, but it's right on Main Street.) Knitting Studio in Phoenixville carries Cascade. I can't remember which brands Lamb's Wool in Lansdale carries, but they have an excellent selection.