[JailBreaker123]

I am currently facing some issues with jailbreaking my 3GS, also without use of the power button, meaning I have to enter DFU Mode. I am using IOS 6.1.3, and downloaded both that and IOS 6 to try and get it working.

However, the first time I tried it, after entering DFU mode and jailbreaking, I got an missing keys.plist, with the 6.1.3 update.

I then resorted to the 6 after multiple attempts, and managed to get it to complete jailbreaking with redsnow, but then after 10 minutes or so of showing Downloading Jailbreak Data on my phone, the screen soon turned off and wouldnt turn on, meaning I had to plug it back in.

Sorry Im a bit of an amateur with this stuff, but does anyone think they could help?

[natasftw]

Meaning you have to enter DFU mode? Not having use of the power button doesn't dictate a necessity for DFU. The jailbreak dictates that. However, if you don't have a working power button, you might consider fixing that before working with jailbreaking. You'll want the ability to enter DFU later if needed. It's possible you'll lack that ability without a power button if one of a few things goes wrong.

If you're using 6.1.3 for the jailbreak, redsn0w won't let you get anywhere. It'll tell you the IPSW isn't supported. I'm not sure how you think you were using 6.1.3.

Resorted? You should have been using the 6.0 IPSW from the start.

Meaning you had to plug it back in? Why was it ever unplugged?

Either your description is entirely off, or you're jumping into this without any idea of what you're doing and you should look through these threads to get an idea of what you're working with before just jumping in.