Kinda curious as to what the indicators of a worn out transmission. Are there sounds, slipping out of gear, etc or other indicators of a problem or is it catastrophic failure?

 

the most common symptom of transmission trouble is a very loud sucking sound from the wallet of the owner as all of his cash is sucked out.

 

I thought that was the symptom of owning a boat...

 

I'm having some issues during the first 15 minutes of driving on slow roads, around 50kmh. The transmission keeps on switching between 3rd and 4th (or 4th and 5th) gear. These issues disappear after ca 15 minutes. I read in another thread about someone with the same experience, and the "gear indecisiveness" was cured by a transmission oil- and filter change. I plan on having this done as soon as possible.

Unfortunately I don't have any history of the car, so I don't know if the tranny oil and filter was ever replaced. I've also heard voices that say if the oil was never changed, it might be risky to change it after 100k miles...

 

a big 'bang' going from 1st to 2nd, clunking into other gears, slipping...aka, keeping a high RPM but won't shift, then it will, refusing to engage a particular gear, likes reverse just fine, refuses to move forward in drive, or if it does...only 3rd gear -> the failsafe mode.

Most could be a symptom of low fluid (excpet the bang and clunk), a slow leak from the transmission pan or connector sleeve may take months before any symptoms start to show, that's why most around here recommend a fluid check, and/or even a fluid change to rule out contamination.