Ok so i'm learning my first solo - Enter Sandman - MetallicA, i know as far as first solo's go this is a hard one, but i like to challenge myself, now i have a couple fo questions:

1. How can one get enough finger speed to play solos is it just a case of repetition or does one need to analyise the things going on

2. How can one improvise / create a good solo; how much knowleadge does it take, as i'm a fairly new gutiarst (in terms of soloing) i have only a basic understanding of notes and couldn't tell you what notes / chords are in what keys etc.
1. Combination of perfect practice and patience. Perfect practice means making sure you are playing at a slow enough tempo were you can control your playing. Making sure you don't make any mistakes, that you are making small and economical motions, that you are relaxed, that you are playing cleanly etc. Playing it perfectly. Then patience for being able to do it for several hours/days/weeks, not speeding up over your abilities and playing sloppy.

2. Experience. In my opinion you have 3 steps of learning a solo.

First step is figuring it out, which should preferably be done by ear. A great ear is a musicians best tool and helps you with learning stuff, improvising and composing. However since you are fairly new maybe you should start simple with learning by ear, and learn solos via tablature.

Second step is learning how to play it. Actually practicing it and being able to get it down. My advice to your first question applies here.

Third step would be to analyze the solo, seeing how it relates to the key it is how the chords it is being played over affects the sound. Analyzing solos is great if you want to replicate stuff you learn in your own playing, especially combined with a good ear.

Hope that helped.
Best Regards
Fusion and jazz musician, a fan of most music.

Quote by Guthrie Govan
“If you steal from one person it's theft, and if you steal from lots of people it's research”

Quote by Chick Corea
"Only play what you hear. If you don't hear anything, don't play anything."
Regarding technique, short highly focussed exercises that address a single specific issue will almost certainly produce far greater results than a full length solo. Consider taking one small section that you are having trouble with and make an exercise out of it. Work with a metronome and try to identify what could be better. Smaller movements in your left hand? Your right hand? Are you picking too hard?
This might sound really dumb, but I come up with most of what I consider to be the most innovative solo's when I'm in the shower. I'll usually just sing the solo either in my head or out loud. As an inexperienced guitarist i feel this will most benefit you because unlike a professional guitarist you wont actively be able to express what you hear in your head to come out of the guitar. So I'd recommend to you to sing the solo's, and if you like it, record yourself singing it (sounds stupid). Then listen to yourself singing it, and figure it out on the guitar.