1990 626 2.2 Auto - Speedo stopped, hold light flashing
 

Hello friends,

I've browsed this forum a few times when making minor repairs on my 1990 model 626, but I've found no results for this issue.

The speedometer is not responsive, nor does the odometer tick up. The tachometer and the rest of the dash work fine, and the car still runs and drives fine. I wouldn't be driving it like this, however I was mid-drive when I realised it was alleging I was driving at 0km/h.
The hold light is also flashing. However the car is still running and shifting gears without issue.

My reading shows me there is a cable running from the speedo to the transmission that is likely the issue, however I don't know how replicable that part would be for a novice, nor whether that will be the source of my issue.
All other info I have found suggests taking the car to a mechanic, which would be ideal, however the car will require re-registration in 5 weeks, and the mechanic's wait list is currently 3.5 weeks. If the fix isn't cheap and/or quick, then I don't really know if I can justify the cost to fix it, given it's not in good condition and is simply a second car for me.

Any advice? Ideas? Anyone else experienced this issue? Any ideas on fixing it?