The infinity project as a whole brings permanent CFW to devices like the PSP 3000 and PSP Go. These devices in the past weren't able to do this, you used to have to turn it on and then load the CFW every time. If the device ever fully turned off, you'd have to load the CFW again. You were however able to put the device in to sleep mode and you would retain the CFW. - With infinity, you don't have to worry about any of that, it is a permanent CFW designed for every PSP model on the latest 6.61 FW.
If you want to install infinity, then use the video which is within my zip that you have downloaded. That is an exact tutorial on how to set up, configure, create your CFW and install it successfully.
As for wanting to download PS1 or any game for that fact, it doesn't matter whether you use infinity on the latest firmware or any other method to get CFW on your PSP. The outcome is always the same, games being able to be played from memory stick; PSP, PS1, Mini's, emulators etc. I would advice upgrading using infinity since this is the latest firmware. As for PS1 games, the PSP store is now shut down, so obtaining them; you will have to do some googling.
If you get stuck, just give me a shout.