Yes, expect them to leak if they aren't stored vertical. And the hydraulic fluid in them is not easy to clean up if it sits for any amount of time beyond a few hours. I can't get it out of my concrete in my shed.
The stock jack in my 97 D1 had a plastic body. Found out the hard way - I was tapping the base plate with a little bit of load on it and I missed and hit the body.. Cracked like a champ and spilled oil everywhere..