I want to sand the end of my corian counter top back about 1/8 inch. I need to get my refrigertor in and I need to get it back about 1/8 inch.

Carbide bit and a router. Sanding, if necessary can be done with sandpaper using eventually 2500 grit or finer.

I'm with KISS, sanding will take forever and you won't get a very straight edge.
If you don't have a router, Harbor Freight sells a trim router for about $21. Only runs at 20,000 rpm but not a bad trim router. A one half inch carbide bit with 1" cutting edge will cost you about the same. Glue a guide to counter top with hot glue. You won't be able to get completely to the back edge, that you can sand.
If Harbor Freight not convenient, order online.

Harold and KISS are right on.

To do the last bit by wall u can use a right angle grinder(with great care). These can be rented at most big box stores.

Chuck