marking seams would take forever, and stuff. also, how can I reduce polys in the model? It’s for animating, and the polys seem too high.
well, i cant help on the unwrap but i do know that blender has a reduce poly script in the mesh script window. hope this helps with your poly problem! 
You call that a “really high-poly model”? chuckles
I eat models of that res for breakfast!
…ok, enough nonsense.
First things first, in the future you’ll want to avoid applying SubSurf modifiers your mesh until the final stages (if at all). Keep them on. But don’t apply until/if you need to.
For selection, if you do a [Select] > [Edge Loop] (while at least 2 verts are selected), that will select an entire loop if the geometry forms such a loop. This should work for things like limbs.
In this case it still may take a while, but pressing [b] twice will enable the circular selection tool (I forgot what it’s actually called). Then you can “paint” a selection of just the verts you want (you’ll need to zoom way in). [MWheel] to resize the circle, [MMB] to deselect.
This is a quite simple model. Try to make a lower poly model by just placing a quad in the center and bo extrude outward to follow the shape of the model. Animating with this amount of polys for a simple shape is quite demanding. You have probably used sculpt tool. For Uv place seems to cut of parts of the model into easy parts. One around the arm above the hand, one to cut of the arm etc. Put seams in edit mode with ctrl + E menu. use line or vertice mode and hold alt while selecting to get loops marked. it is an easy model to uv map. Shapes are what makes uvs complicated.
But really make a new simple version with maybe 1000 polys, it would be enough to get the details. Push z to et wireframe and view the high poly one behind the box you use to get the shape of it.
The only difference between unwrapping a model wit applied subsurf modifier and without is in time. You need much less time and processing power to unwrap lowpoly model. So you can follow the same edgeloops in highpoly model as you would have marked in lowpoly.
In this case, there is no need for such dense mesh, because there aren’t any details modelled, but it is possible to unwrap this mesh also.