i have a really strong gas odor inside my car on 2004 Nissan Maxima

i am getting codes p0300, p1574, and p0057 my husband changed o2 sensor lastnight so i went to do the code again, same code exept for this time it said heater control circuit low, the first time it said downstream rear, i did go to two different places to read codes tho, please help did he change the wrong o2 sensor?????

Asked by for the 2004 Nissan Maxima