Transmission Troubles?

My girlfriend has a 2000 Hyundai Accent GL. It has a 1.5L engine and automatic transmission. It also has 92,486 miles on it.

Today we took my girlfriend's car to "town" which is about 14 miles from where I live. Going into town, the car drove fine on the highway (55 mph) and around town (30 mph - 40 mph). About halfway home (again on the highway), the car began to exhibit issues I believe are transmission related. Until now, everything with the transmission has been fine (we've only had the car for 2 years and looking back at the repair records, there is not sign of transmission troubles prior).

So, here's what I have noted:

- After slowing for a vehicle entering the highway, the car had difficulty regaining speed.

- From a standstill, going up a hill or when gassed to pick up speed, the car seems to be taking longer than usual to shift.

- The engine does seem to be working a little harder and is a little noisier (on takeoff, going uphill or regaining speed) but the RPM's are up only slightly (maybe 200 RPM's tops currently).

- At cruising speed (55 mph), the car drives fine and the RPM's are normal.

- At a standstill, the car shifts through its gears normally (Park-Neutral-Drive-Reverse).

- I think the car shifts a little better with the overdrive off but my girlfriend says its just me.

- The transmission does not slip or jerk when shifting.

Plan of Action:

Over the weekend, I plan on changing the transmission fluid and transmission filter on the car. I am not sure if this has ever been done? I am just worried this will not solve my problems. Any suggestions? Thank you in advance!

 

I know this thread is a year old, but I see no potential answers and no follow up. I'm always curious how things worked out. This sounded like the ole' 0374 tranny blow-up in the making.