1998 Toyota Camry I have a few questions on check engine co

Computer problem
1998 Toyota Camry 6 cyl Front Wheel Drive Automatic 119k miles

my 1998 camry v6 has the check engine light on and I had it code read at aamco. The codes it threw were for the egr valve and evap vent solenoid. I read on another website that you could replace the egr valve modulator and most of the time this fixes the egr problem. Is this true? Also I was told that you can only get the evap vent solenoid fixed through the dealership is this true and if not do you know where I can get it and how hard these items are to replace? My brother has been a mechanic for 20+ years and he told me to try replacing my gas cap and removing the negative battery cable to see if the light comes back on how likely is this to work. Any help is appreciated