There isn't much point in going through any calibration before you're sure it has been cleaned of any electrolyte.
Once correctly cleaned I doubt it will need calibrating at all.
If it were mine I'd be making sure that the supercap is discharged or removed, remove shields, LCD, switches and wash the lot down.
As an example the DMM in this gallery
https://photos.app.goo.gl/uCUmZvgM6NLxzHAJ7 was in quite the same case as yours, after several good toothbrush scrubbings in water, soap, vinegar, much rinsing, and a final scrub with WD40, this meter was back within tolerances.