Car is not shifting right and Honda dealer says code for ''throttle positioner failure'' is showing up.They say l have to replace ''throttle body'' for $475, anyone know what a throttle body is and if this may cause it to not shift right?The RPM gets really high before the next gear kicks in.

Says transmission seems to be okay.
Would someone who can not even change their own oil be able to do this?l have no clue about cars.

It is automatic and it runs well except the shifting gears problem.

they r referring to the TPS, or throttle position sensor, which is an electrical sensor located on the side of the throttle blade shaft. ur throttle body is the inlet into the intake manifold form ur air intake tube. the throttle blade is actuated by the throttle cable, which is what u pull when u press the gas. the TPS tells the engine computer how open the throttle blade is so it can properly trim the fuel tables & ignition timing, as well as determine engine load, which is used to tell the transmission when to shift among other functions. ur car is an automatic, correct?
you can replace the TPS sensor by simply unscrewing the old one, & replacing it with a new one, making sure that it is inserted exactly like the old one was.
if u do not feel comfortable changing the electrical sensor, u can go on ebay, or easier, a local junk yard/auto recycler (check the yellow pages) & find a stock 2002 civic throttle body for ur size engine very easily, as many people change them to aftermarket throttle bodies. should u go this route, & decide to replace ur entire throttle body with a sued replacement, make sure u buy the gasket for it as well, go to a NAPA, Discount auto, or pep boys & buy it. also, take a picture of ur stock throttle body & note all of the sensor plugs, vacuum line, & cable hook ups to it as well. does ur car drive normally besides it shifting late? if the TPS had failed, ur car should run erratically, & stutter. because the computer would not know the true position of ur throttle body, & hence the amount of airflow the engine is recieving.

You could do this yourself it is very simple. It would even help you if you bought a haynes manual and the part and just follow the directions. Its very simple.