First off, I have an Automatic 1998 Honda Civic and when shifting from 2nd to 3rd my RPM gauge and engine will rev high for a second then go back down. What could the problem be, Thanks in advance. If you want to know anything more specific ask :P
Also I'm new to working on cars : )
-cory

Change the transmission fluid and see if the problem goes away. If it doesn't, I suspect the transmission needs work. Clutch packs may be shot and slipping, causing the rpm to increase between shift points. Transmission fluid should be changed every 24,000 miles or 24 months, whichever comes first.

How should I go about changing the fluid? Should I do a Flush? Just change the Oil and Filter by draining? I've been researching which I should do and nothing seems definitive, also I have 104k miles on my automatic 1998 Honda Civic LX? Could it reving high from 2nd to 3rd mean there is debris in the transmission which would make a flush bad right? Help.

Follow the standard procedure of removing the yellow dipstick and transmission drain plug, after the transmission is brought to operating temperature by driving the car. Change transmission filter, if so equipped. Capacity is often 2.9 quarts. 18 x 1.5 mm drain plugs are usually tightened to 36 lb-ft. Refill with the proper ATF and check fluid level on the dipstick, when the transmission is at normal operating temperature.