2000 Ford Expedition Transmission problem

Shifting has become sluggish even in gradual acceleration. On the dipstick, the fluid appears red with lots of bubbles. When I clean and re-insert the dipstick it comes back out with fluid way up above the cross-hatched area where it should be so I've been fearful of adding fluid.
Once yesterday, it took several seconds for the vehicle to lock into PARK in a parking space!
The vehicle has 198000 miles on it but the engine was replaced in 2006 at ~140K miles. Most of our driving is not rough but it is stop-and-go.
Is fluid drain, pan removal, filter replacement, re-sealing and re-filling a job that you'd recommend for a driveway mechanic?
I change oil and brake pads in the driveway but I've never touched a transmission.