1) Always safety first - will you take precautions? Electricity can kill you.
THIS IS NO LAUGHING MATTER!
a) NEVER contact any exposed electrical parts when it is powered on.
b) ALWAYS ensure that ground (earth) is properly connected to mains, your circuit board, and the metal amplifier case.
c) ALWAYS use a multimeter after project completion, to ensure ensure switches, the metal case, and anything you may touch has not short circuited.
2) Under 18? - talk to an adult with electrical/electronics knowledge and ask them to check that you have sufficient knowledge and tools to complete the task.
3) Tools - you need to be willing to invest your money in the proper tools in order to get the job done right.