Its straight forward spray the bolts with penetrating oil first(liquid wrench,pb blaster,wd40) let sit an hour or so and it really helps if you have access to air tools but if not more then likely you will need a breakerbar for the exhaust bolts
The o2sensor is easy as well just depends wich one you want to change out
A o2 sensor socket is handy autozone rents the o2 sensor kit