gas safety valve on oven? Can i replace this myself?

Hi, our oven doesnt work at all…the repair man was here last night and said that the gas safety valve was shorted out, so we need a new gas safety valve and both ignitors replaced…is this is the kind of thing I can do myself or should I have him do it (he quoted $300 for the job…$150 for the gas safety valve alone…) ?
Thanks so much!!!