That (changing bearings) may be an overkill ..
According to this doc below, new bearings are not really needed.
http://f1.grp.yahoofs.com/v1/ANfZThM...comparison.pdf
(in case the link doesn't work, try this:
http://tech.groups.yahoo.com/group/E...e%20Tinkerers/
The docs are at the bottom of the page)
It is my personal belief that all those kits are not really necessary in most cases.. waste of money, until you are really sure if you have a problem (and what it is, of course).
What may be necessary is cleaning, and adjustment...