Swapping steel for aluminum wheels will make a noticeable difference. Bottom bracket won't, my impression is that most LBS that are not C&V friendly consider loose ball bottom brackets hopelessly obsolete and that they should all be changed out as a matter of course. I agree w/the previous poster, unless you are setting off unsupported for Tierra Del Fuego, engaged in hi-level competition, etc, just grease it up. A lot of the bicycle industry sells to people's need to view themselves that while perhaps they aren't actually engaged in such extreme activities, they are suitable candidates for doing so if they chose.

Anyhow, as a matter of course, I usually just change out the bearings, they are pretty cheap at loosescrews.com, on most loose bearing components when I open them up to relube. Get grade 25 bearings, it is a cheap luxury, much cheaper than a sealed bottom bracket.