I'll post this here in case someone comes along later looking for the solution.
Mercury is quite valuable & a lot of places offering to take it off your hands for a considerable fee as 'hazardous material' are just going to take it down the road & cash it in at an industrial metals dealer.
It is toxic if enough is eaten or otherwise absorbed, so don't play with it (it is fascinating stuff) but it was used for medicines into the 20th century so its less deadly than, say, plutonium. If you are over 30 or so, you would have been walking around with a fair bit of it in the amalgam fillings in your teeth, but that is being replaced with epoxy 'ceramic' now.
The body does eventually excrete the stuff, just very slowly. In the gold fields mercury has been replaced with a cyanide process industrially, which strangely enough is also toxic and takes years to recover from.
