I just upgraded to play online also. I'm not sure if there is an easier way, but it worked.
-You're gonna want to download the 3.50 FW (found
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-Once you get it downloaded, jailbreak your PS3 again like you did to get 3.41.
-When you get to the part where you would normally input the 3.41PUP, replace that with the 3.50 FW and install normally.
It'll take you through the same process again and it should load up 3.50 on your system.
It's a little vague, but if you jailbroke it already, you should know what I'm talking about.
Just follow everything else normally and use DNS to play online