2003 Impala LS w/6500 miles_popping noise in steering column

Just picked up a 2003 Impala LS with 6500 miles on it. Previous owner was 93 yr old lady who recently passed away. Car was always garaged and appears brand new. The only problem so far is that occasionally theres a popping noise that can be felt through the steering wheel. Ive felt it when turning, going over a speed bump, or rough pavement at low speed. I was told it could be a steering coupling that needs grease or replacement. Any comments regarding difficulity of repair, cost to have it done, or suggestions appreciated. Thanks, Gary

Possible intermediate shaft.....should be a TSB on this....

If indeed that, some info...
http://impalahq.naioa.com/TSB/TSB01-02-32-001A.html

That TSB has been changed so many times, with different fixes.....

.. and none of them are particularly effective, lasting about a year or so. The "plug" was supposed to prevent lubricant loss.
It doesn't.

That plug is not left in the shaft....only used to disperse the grease, and then removed.....

First, you replaced the shaft......then next bulletin, you greased it....then another bulletin, you replaced it again, then greased it again....then a bulletin came out, depending on color of shaft, whether you replaced it or greased it.....crazy....

Different models had different fixes, also.....and different TSB's....