Swallowfurry- Next time, post a descriptive title so that members and staff will be able to address your issue more quicker.
As for installing 5.50 GEN, there are three updates: 5.50 GEN-A, 5.50 GEN-B and 5.50 GEN-B2. You are right when you say that all three of the updates goes to /PSP/GAME. Just overwrite any old files.
5.50 GEN-A
5.50 GEN-B
5.50 GEN-B2
When you transfer all three of the files, reboot into recovery. (Reboot while holding R)
Go to Configuration > Game Folder Homebrew. Press X to make it say Game folder homebrew <5.xx kernel>. Once you do that, exit recovery.
When you get to the XMB, go to GAME>MemoryStick and launch the updates in this order:
5.50 GEN-A, 5.50 GEN-B and then 5.50 GEN-B.
It should work just fine.