I have sand and dirt between the rubber gasket (shim?) and the glass that I would like to clean.

Is this as straight forward as it seems?  Anything to watch out for putting it back together?

Thanks!  Steve

Yes it is, you will find the rubber gasket will be stuck to the glass like it was glued, it wasn't, just time and heat has made it that way.  You will need a putty knife to break the seal.