Can you download and apply a patch for a retail disc game?

I bought God of War after 5.50 came out, so I was never able to connect to PSN to download the patch.

Now that HEN is out, is it possible to download the latest patch that still uses 5.05 and install it and have it work? Would I have to rip the game first? I heard that retail saves wouldn't be compatible with ripped versions, is that true?

Thanks in advance.