This something you should be able to find in like 5 minutes. http://www.csulb.edu/depts/enrollment/registration/fees_basics.html If this doesn't answer your question, you should contact the school.
I highly doubt the schools are going to communicate with each other. Also, how would one school knew you applied to the other. Talk to the school you want to go to and see if they have any advice. You can rescind your offer from your first school, but they probably won't be happy about it.
What I did was just go through each class I've taken and go back 60 units. There are gpa calculators you can use to put in your units and the grade associated with them. For example, an A in a 4 unit class impacts your GPA more than an A in a 3 unit class.
As said, if you already denied the place you want to go, then you will most likely not be able to reverse that decision at this point in time. If you got a second offer at say your number one choice, then you can probably accept that and inform the institution you already accepted that you will not be attending. They probably won't be happy about it, but just be professional, and it should be fine.
That's what you get to say in your statements. You realized that Engineering was not for you and decided to change your major into whatever you have now.
Just make a budget. Take your monthly income, subtract overestimated expenses, and you have a budget. Some things I put in mine. Don't forget to take any other costs into account like apartment deposits, moving costs, ect.
Rent
Utilities
Mandatory Health Insurance
Loan Repayments
Groceries
Car Insurance
Fuel
Phone Bill
Slush Fund
Car Payments