Why use a single field for all three? It will greatly simplify things if you put three search fields across the top of your layout--one for each type of search. That allows you to use different scripts with each field to produce the desired results.
It's certainly possible to use a single field for this, but only if you can put togther if steps that reliably distinguish between each type of term entered into the field.
Note such a script would have to determine that R280 is a plant code and R280GC is a SKU.