1. If I put the same algorithmically generated problem in two different homework sets, will a student see a different version in each set?
Yes (with VERY high probability :-)). The actual problem is determined by the template and by the seed. Changing the seed (which you can do when you edit an individual's homework set using the Hmwk Editor) will change the parameters of the problem. If I remember correctly there are several 100,000 seeds.
2. Where do I find documentation on parameter settings of dynamically generated graphs. The PG code snippets are useful templates, but, for example, I did not find if or how I can specify where to put grid/tick labels. (Can I label only specified tick marks? Can I label with multiples of pi?)
The pod documentation will help some: http://webwork.maa.org/doc/cvs/pg_CURRENT. The files PGgraphmacros.pl, and WWPlot.pm have the most documentation. There is also some in Circle.pm, Fun.pm and Label.pm.
http://webwork.maa.org/wiki/Graph_Object_Documentation is where new Graphics capabilities are being planned and documented.