Toyota Repair: 1996 Toyota Corolla ERG replacement, toyota corolla, oxygen sensor

Question
I have a 1996 Toyota Corolla DX, Automatic transmission. The check engine light is on.  The Toyota dealership mechanic determined it was probably the EGR Valve and perhaps once he got in there it might need an oxygen sensor. How hard is it to replace these components? I am mechanically inclined however I do not have a shop or specialized tools.  I want to fix it myself if possible.  Thanks in advance!

Answer
It sounds like the mechanic is guessing and doesn't know what the real problem may be, this may cost you more money than necessary, I need to know what the trouble code(DTC) is and I can help you figure this out and see if it is something you can do yourself.