Shellac in good condition can handle a wipe with a damp cloth. Before the days of microfiber or artificial leather, they recommended a well wringed up piece of goat or lamb leather for cleaning shellac furniture like a table top. Waxing and polishing have always been recommended too. As long as it's not flaking off or top layer on decals are worn off shellac can handle a careful cleaning. S'ewing m'achine oil is often recommended as the gentlest way about it, but as long as it's in good condition a damp microfiber cloth should not affect shellec. A resin type car polish will further lift up dirt and grime, leave a protective film making it shine like almost new. Since it's in such a good condition to start with it should be an easy job, it just takes a bit of care and time. Dings can be improved upon, but is a bit more work.
It's amazing what you can do to an old damaged case though. As long as all parts are there it's well worth a bit of time and effort to piece it back together; glue back lifted veneer, replace a few screws, reupholster it, etc., but with a lot of parts missing parts I don't know if they can be tracked down that easily.