Replacing the Instrument-panel glass is tricky, however it can be done with some very careful measuring, a good glass cutter, a good cork-backed steel ruler, a "Fine" to "Medium" wet-stone (the bigger the better) and some patience. The specific ruler-type gives a non-slip/raised edge as a good cutting guide. I've used this procedure with excellent results.
A glass shop can supply you with a piece of 3mm? glass. Take the seal with you. Avoid using Acrylic, Lexan or any type of plastic. These will scratch easily and may deform in extreme heat conditions.
There is a small rubber perimeter seal that caps the edge of the glass. The glass and seal must then drop into a recess on the inside of the black housing. The white internal housing in turn, sits in the black external housing and actually squeezes the rubber seal when the two are screwed (8? small screws) back together. If the fit isn't correct you will break the glass. On my repair everything appeared to go back together correctly but the next day I had a "stress-fracture". I didn't have the glass and seal in the recess correctly ! The dimensions of the glass is critical. The recessed lip of the housing is very narrow. If the glass is too big by even a 1/32", you won't get it to fit. If it's 1/16" too small, the narrow seal will have minimum contact with the housing and might move around enough to possibly allow the glass-edge to pop out. You can get the width and length from the existing pieces or by measuring the housing. I have tried to use a template and for me; it was a complete waste of time. Buy enough glass to potentially make several in case you break one or are otherwise not satisfied with your 1st/2nd effort. You'll likely be fitting/adjusting until you're satisfied with the fit. The stone is what makes this a practical job to undertake. It will smooth and straighten the four sides, it will remove the razor-sharp edges and it will provide the means to round the four corners. When "stoning" the glass keep the stone wet with some WD-40, or LIGHT -oil or even a few drops of solvent. The stone MUST be wet and is very effective at removing material very quickly and efficiently. Take your time, wear your gloves and safety glasses, and good luck.
Further Note; Trust me on this one !!! To clean the dial faces if required DO NOT use solvents, cleaners, soaps or the like. Use a clean soft cloth and some "spit" ! Yes I said spit. DO NOT touch the needles ! DO NOT start "bending" things. 30 yr+ needles are as fragile as an Egyptian Mummy !
The "spit" thing. That's a trick from a man who repaired instruments for 32 years.