I've got a few issues.
#1 first and second gear are kinda rough and take a few extra seconds to catch up.
#2 my reverse gear no longer engages. So no reverse at all I have to turn the car off fully in order to move it back. Neutral drives the car forward as though it's in first gear. Won't upshift from there.
#3 my cluster gauges don't give proper readouts. They all engage sometimes except the thermostat which almost always works properly or at least gives a proper razor. Lights all turn on when given power and such but the speedometer and tachometer don't read properly. If I give the dash a smack the speedometer will fix itself but not the tachometer.
Details
New fuel filter
New starter
New alternator
New ignition module
Soon to change out valve cover gaskets (small oil leak on pass side.)

 

Sounds like a fluid and filter change is in order for the transmission.

Locate and check all of the ground connection points on the car. There should be a couple or three under the dash. Usually loosening and retightening them will reseat them to give a good contact. When troubleshooting any electrical issues, checking for proper grounding is the first thing to do.

 

Do you really think all the transmission might need is a servicing?

 

Could be.. The fluid will not last forever and the filter can get clogged over time reducing fluid flow. Restricted fluid flow will cause the trans to slip as the valvebody cannot get enough fluid moving through the systems to lock up the clutch packs. This is not good on the clutches as it causes them to get too hot and degrade even quicker. Fresh fluid and a fresh clean filter can do wonders sometimes. That is if the clutches are not already fried.