After 2 stressful hours, I was finally able to go through Solar and choose my courses. After finishing this process, I was sent to the screen where I was able to print the summary of my courses, and at the top I have values such as the student number and confirmation number.

I attempted to click on the Payment Agreement, but the system crashed because of overload. Does this mean my application went through, or could it have been interrupted? Would I have to log on again and go through the Payment Agreement?

If you saved your selections in SOLAR and got the confirmation screen then yes your choices went through, but your payment agreement did not.