Questions before I take my car in

[carl669]

I've got a 99 Solara that's due for an emissions test in the state of Washington. My engine light came on a while back, but I never got around to having it looked at.

Since washington does the OBD tests, i needed to get some things taken care. I bought an OBD tool and the following codes are showing up:

P0135 - O2 Sensor heater circuit
P0402 - Exhaust Gas Recirculation Flow (EGR) Excessive Detected
P1410 - EGR Valve Position Sensor Circuit Malfunction
P1411 - EGR Valve Position Sensor Circuit Range/Performance

my question to you all is, would I be able to make any/all of these fixes myself? i haven't done much work on my car, but i can be pretty adept when I need to be (read: when it saves me a lot of $$). i also don't have a ton of time to sit and make repairs, so that is a consideration. if there's a couple quick fixes i can make and then take the rest to a mechanic, that would work as well.

if you think it's easier for me to just take my car in somewhere, any idea of how much I should expect to pay?

thanks in advance for any help. let me know if there's any additional info i can give to help get my questions answered.