CEL went on today need some suggestions

hey all
When i started my car today the cel went on. i checked for the code and it shot out two codes.
this is for a 96 240sx
the first code is a 707 , rear o2 sensor. Ive heard that the rear o2 sensor doesnt affect gas mileage , only the front one. Am i right or wrong? should i replace it

the second code is 1302 , the fsm says that its the map/baro switch. i checked all the hoses and found that my absolute pressure sensor is broken. there is a hose that goes from the map/baro switch to the absolute pressure sensor. the hose that was going to it broke off and was just flooping around the engine bay. and it wont re atttach to the sensor

my second question is , Is the second problem causing the first?

i called nissan today and they wanted like 300 bucks for the sensor :rolleyes:

any suggestions anyone?
thanks