1.7 GHz Intel Core i5 10.7 Macbook Air Water Damage... still works... Battery issue

While on a flight in June 2014, the guy next to me put his drink in the gap between the tray and his cup spilled liquid below including on my macbook air which was in the pouch. Unsure of whether there was liquid damage because it was in a protective laptop sleeve, I turned it on and it would work for a minute or two and then turn off.

The next day I took it to the Apple store and the Genius Bar guy could not determine if there were problems. However when I went to use it over the next week or so, it exhibited an unresponsive/slow trackpad which I assumed with an expanded battery due to liquid damage.

After that resolved itself, the only issue I could point to is that the battery loses its charge at an exponential rate (will go from 100%-20% in an hour or two) and it takes substantially longer to charge to full than before this incident.

Went to another Apple Store a few weeks later and upon opening the Air Genius Bar said

Issue: Customer states device had liquid spilled on it. Afterwards, machine is showing multiple charging and battery issues. Steps to Reproduce: Verified battery failed and has liquid damage to battery. Corrosion appears to be present under logic board. Proposed Resolution: Send to depot for Tier 4 liquid damage repair. Replace all damaged parts.

And gave me a $755 quote to have it repaired. I said I would take my chances because for that amount, I'd rather buy a new macbook air entirely. He said it would be a matter of time before the computer would stop working all together.

With that being said, its now 8 months later and the Air is still working, however, I basically always have to have it attached to the charger.

I'm wondering what potential issues I may run into order a new battery via eBay/Singapore and swapping it out via iFix tutorials and the such. Is it possible that electricity is currently running through some of the corrosion on the current battery and if I swap it out, it could brick the entire laptop? What other scenarios could exist where I may better leave everything alone.

Thanks.