Yes, you'll need a lv2diag.self file along with the PS3UPDAT.PUP. I think they both need to be on the root of the USB drive. There are several lv2diag.self files out there, so you need to make sure that you have the right one for your needs. I know of three of them: one to exit FSM, one to fix RSOD, and one to flash a .PUP file. Connect the USB drive before you turn on the PS3. I guess you can give the NOTHEROS.PUP a try and if it boots to the XMB, then install and run rsodfix.gnpdrm.pkg.
Opexone78: Are you having RSOD problems with just that one game?
There is a risk of bricking your PS3 permanently with the NOTHEROS.PUP, so make sure you read up on it.