In all fairness the kit came with instructions, as shown below. If certain repairs are beyond your scope of expertise, then you need a live tech in your home to do the work. The first repairman already told you the problem and he was right. Don't get in over your head just to save a few bucks on repairs. There are many other simple repairs that were made for moms, this is not one of them.
Since the problem occurred only 3 months out of warranty, your best bet would be to call GE and tell them you already bought the parts if they will cover their defect by sending a tech out free.