Shouldn't this be a two-way share? I mean, if I setup a Homegroup on the PC and the Surface joins the Homegroup, shouldn't I be able to see shared files and folders on both machines? My Surface can see the shared libraries on the PC but the PC can't see the libraries on the Surface.
My guess is that your Surface has Network Discovery disabled in your Advanced Sharing Settings, take a look at that. Do a search for "advanced" and you should see it under Settings as "manage advanced sharing settings".
As for sharing files I have a Windows Home Server on the network which makes it really easy to do from any device on the network.
Edit: Ha, I take that back...I didn't realize how much they've stripped from RT,sorry.