Now it's really noticable when I try to put it into 6th gear. From 5 to neutral to 6, when you're trying to put it in the 6th gate, there's quite a bit of resistance (I am holding the clutch all the way down). Almost feels like there's something kind of blocking me from putting it in there.

 

i'm not sure exactly, but i remember reading somewehre on here about locking out of 6th as a symptom of gear skipping. most people rip through the gears and at 3rd gear you're going fast "enough" so u pop it into 6th, but that destroys the 6th gear synchro or something because the difference in speeds between two somethings is too great and...

i think ur synchro is worn. try the synchromesh fm. it could help, but it wont fix it if they really are worn out.