I would never touch this one with chemicals.
Grade it? I wouldn't, only because the cost would outweigh the value gained. But with the oxidation going on in the error zone I'd put it in an airtight or something similar, which might include the slab from a grading company. So you are likely to not gain dollar value from slabbing it, but since it needs to get air tight anyway maybe you choose to slab it for that reason? Your call, but it won't add value as the coin would sell just fine as-is. Note: PCGS
charges $65, in addition to grading fees, shipping and insurance, for an error coin. That's a like about $100, for a coin that may or may not get close to that when sold. My general rule it that it needs to pretty much be a $300 error coin in at least MS-65 condition before I'll slab it as so much value goes to the grading company that the only way to overcome that is with a really high grade.