02 avalanche drive shaft

Hello. I just have owned my Avalanche for four years now. And i just had
my universal joints replaced when I picked up my truck. I was told that
the yoke was bent and that i may need to have that fixed. And that they
straighted it as best as they could. I did not know how bad that it could
have been untill I went about fify yards down the road I could feel  that
there was some vibration throught the stering wheel. I never had a
problem prior to them replacing the universal joints no vibration no issues
at all. When I got the free way to see what was going on it was like sitting
on a massage chair. It scared the heck out of me. When I went back the
owner took it for a ride around the block and said that it is possible that
the joint being worn out would keep it from vibrating and when the new
joints were installed is why I am having this problem. Because the new
and square.  
Is there any truth to what I have been told. Because they want 400$ to fix
it. I didnt do I went and bought another complete shaft and installed
myself and I am not having any issue's whatsoever.. so is any truth to
this?? Thanks