Questions about changing Trans Fluid & Filters

I had my transmission fluid changed at 35k at Ford and at that time they changed the internal filter and external inline filter. Now I have 76k on my truck and I am going to be changing the trans fluid again. I plan on following the steps in the FAQ and I don't plan on changing the internal filter. My question is do I need to replace the external inline filter? If so, can I get them some where besides Ford? Does anyone have a part number for the filter if I get it elsewhere?

One more question, can someone explain the benefits of Synthetic trans fluid over dino? I don't tow anything and my trans temps never gets over 190, so is it worth it for me to use Syn. Fluid? Does it help performance wise?

Thanks