Try Alysin (or Alisyn...can't remember the spelling...Dillon Music probably has it...I hesitate to recommend
ANOTHER 
dealer). It is a synthetic. When my supply of Al Cass runs out, I'll be switching over to it, too. A couple drops lasts a few weeks. (I hate taking time out to oil valves).
The black stuff...unsure about that one. Take it back (or take a photo and e-mail it) to the shop and show them. Was there any discoloration before you had the valve job done?[/i]