Uphill is allowed and done by some.
For more workout you could start at GHL too but you'd have to do your own shuttle.
There are several options for Nordic touring if you want exercize. Puffer Pond, Hour Pond, Botheration Pond, The Vly, Siamese Ponds, Buck Meadow. In addition any route that looks doable on a topo is probably doable and may even have a hunters path to follow.
Telebnor Nordic recommend for all. AT less useful in the Siamese IMO. Ed or Shamans opinions probably more valid.
"You just need to go at that shit wide open, hang on, and own it." —Camp