[rondeo]

The first thing I would do is have the FLUID LEVEL checked.
How to check the fluid level:

Car level. Remove LH front wheel and restore level. Get gbox to 35 deg C.
Go through all selector positions 20s each. Place container and remove level check plug. Allow fluid (if any) to flow until it slows to a drip. Check fluid for contamination. Add fluid in 250ml lots until fluid flows again and slows to a drip. Replace plugs etc.

It's not a difficult DIY job. Just the details of the procedure need to be known. A mechanic should be able to do it in 30min? Unless there is evidence of particle contamination there should be no need to change the gbox fluid.

That's where I'd start, then see.

Probable reason for wrong fluid level: human error.