No, you can update direct from you existing installation (as it remains in memory). Just start the new FMCB-Installer with your existing FMCB and uLE from an USB drive.
To start games from USB mass media, you can use USBAdvance, but since this is only an USB 1.1 connection, many games run choppy (in FMV, etc.) and the overall compatibility is not very good.
Slim PS2 SCPH-70004 (v13) w/ FMCB, 3x Sony 8MB, 1x MaxMemory 16MB (Backup card)
I'm not available for FMCB installation service until I can guarantee a processing time of a few days again, sorry.