Im currently thinking about acquiring a player via trade that's in his third year of arbitration.  I've read before that arbing a player three times makes him more likely to test the FA market.  Since we've already entered the Arb cycle and signing him long-term isn't an option at the moment my question is whether or not this player will hold a grudge against me for the 3 trips to arbitration or if acquiring him via trade will wipe the slate clean.  Along with that, would it be better for me to ask his current owner to go to arbitration with him, or should I be the one to take him to arbitration.  Thanks.

Make him go to arb.  After arb, ask him whether the player will resign.  It's not a gaurantee that his stance on resigning will remain the same after a trade, but it usually holds to form, in my experience.  It gives you more info to work with than just guessing.     

You can sign players to LT contracts during arb.    Halfway down the arb page and you'll find it.

If he's worth trading for, chances are he's worth signing long-term.  If you're trading for him, have your trading partner sign him first.  If he won't, offer less in trade.  His value as a 3-arb guy could go way down if you can't sign him.