From a Hobbyist's point of view - it is repairable if you have a lot of time, patience and the right tools. Otherwise, buy an Altek and repin at least J# and J4.

Backglass - try with water first. Use a wet rag and keep away from any flaking areas. If the dirt is not coming up, spray windex on the rag. NEVER EVER direct on the backglass. Try a little bit first, and then more.

Playfield - Nifti and rag. Spray on rag. Then use Novus 2.