Engine light - emissions problem

I'm currently deployed with the USAR and have had my parents drive my 97' Maxima SE from time to time to keep it moving. I've had no problems until the last time they were out and the engine light came on. When they brought it to the dealer to be checked the mechanic stated it was an emissions problem and would require the 02 sensor, vent control valve, and canister to be replaced.

I would like to know how difficult it would be to do this "procedure" on my own? They quoted $450 to do the job, which isn't much. However, I enjoy doing my own work whenever possible. I would appreciate any advice on replacing the above (i.e., how difficult would it be for a mechanically inclined person without much vehicle experience, what would the approx. cost of parts be, etc.).

Thank you,

James White