Stephen,
Whether or not you could "upgrade" the bearings would probably depend on the thickness if the sidewalls. I would check the wall thickness, then get in touch with the good people at FOOSBALL.COM (the generous hosts of this forum). They sell some snap-in bearings made for mid/low end Tornado brand tables that may work for your table, depending on the wall thickness. If not foosball.com also sells what looks like replaement bearings that will fit your table.
And if you do order from foosball.com, I would get a little bottle of fooslube as well. Based on the pictures, I would clean the rods with some windex, dry them, and put a little fooslube on them. The table will feel ALOT faster, and play much better with slick, fast moving rods!
Good luck, and feel free to ask if you encounter any other issues!
Edit: to actually answer some of your questions
Both of the bearings that I am refering to above are not REALLY bearings, but technically bushings. The Tornado bushings ar the 1" snap-in bushing/bearings, the other ones are like the replacements installed by the previous owner.
here is the link to the 1" Tornado Snap bearing
http://foosdirect-store.stores.yahoo.net/fts-110-040.htmlhere is the link to the generic replacement bearing
http://foosdirect-store.stores.yahoo.net/bushing-ts.html (Bushing)
http://foosdirect-store.stores.yahoo.net/chfapl.html (face plate)
the screws can be purchased at your local hardware store.
here is the link to the fooslube
http://foosdirect-store.stores.yahoo.net/fooslube.html