I'm a beginner myself, as i've only tended to small tanks in the past..
I've had beach glass in my tank for about half a year now and everything seems OK. I wasn't sure at first, because I know that older glass contains lead which is harmful to fish.. but I took the gamble, and seems that all the glass is good.
You can't boil it, so be sure to clean it very well first if you choose to use it.
I have a fair amount of it in my tank, as I think it looks nice.. over a quarter of the bottem is covered in the stuff.
No promises though, may want to wait for a more educated opinion. I guess it could carry bacteria or parasites.. as you have to go to lakes and the such to find it.
PS: Check each piece for sharp spots, just to be sure.