Most installations don't need an FM trap, but feel free to run and post an FM Fool report... It will be easy to see if there are some high powered stations close to you.
If you install a trap, it needs to be on the input side of the amplifier.
I advocate grounding the mast and the coax as two equally important but separate steps. I don't encourage the use of isolated ground rods. If you add a ground rod, it should be bonded the existing power grounding system with #6 AWG or larger copper wire. This is to prevent large voltage differences from developing between the new ground system and existing ground system if fault current flows in either.
Here's my stock answer re. grounding:
http://forum.tvfool.com/showthread.php?t=901 (Post #20 is the summary,
http://forum.tvfool.com/showpost.php...4&postcount=20)