What do you mean can barely see the screen ????
Is is dark or is the contrast really weak ?
The button being jammed is very easy to fix, you did not get the rubber back in the correct place so it folds and activates the button all the time.
Everything has its place and it has to go back exactly as it was or it works all screwy.
Look at the tutorials about disassembling the PSP. Pay very close attention to the position of things
before they come apart. Like I said they have to back together EXACTLY the way they came out.
When you take something as complex as this apart you have to examine everything carefully to see how it works.
Take your time, do not get frustrated.
Hey this stuff is supposed to be fun, learn from it.