Is installing new AirPort card an option?

Hello,

Last week, I spilled a small amount of water on the upper left side of my Macbook keyboard (I know, I know... enough self-flagellation to last a good while). Not knowing what to do, I turned it on again. Everything seemed fine, so I worked on it for a few hours until suddenly the keyboard made weird buzzing noises and it wouldn't turn on again. Then, I searched these and some other forums on a different computer for tips, turned the Mac upside down, and removed the battery. Last Thursday, I took it to the Mac specialist at my university and they let it dry it. Luckily, the specialist e-mailed me yesterday and when I picked it up today(a week later) everything seems fine--except now my AirPort card does not show it--it says it isn't installed. Searching various forums again, it seems that the AirPort card is on the left-hand side of the keyboard. So I surmise that it is kaput.
The substitute tech who is filling in for the Mac specialist (who's now on vacation, of course) insists that I erase everything on my computer and reinstall the system. The tech is really insistent about this, but users on the forums indicate that the reinstall does not work if the AirPort card is indicated as uninstalled (reinstall works for computers that register the card but cannot connect up with networks). I am loathe to do this, especially since all my e-mail is on here and archiving, recovering programs, etc. would be a huge pain. The internet works via an ethernet cord (I am using it now) and I would rather just install a new AirPort card. I searched the net for two hours today and could not find out how to do this, except on ifixit.com. But I have AppleCare and the forum users have indicated that installing a new card myself will void the warranty. I wouldn't know how to do that even if it were not the case. Am considering a USB external thingamajig but would rather have everything back to normal. Apparently sending it in for repair would take >2 wks and cost in the neighborhood of $750--no good for a student with final papers due. Before I got my laptop back, I've been writing assignments in my dorm's creepy basement cluster, where a homeless man came by last night and shouted...sigh. Any ideas?
Thank you so much in advance, and for reading this epic! Just wanted to make sure all pertinent details were included. Have had Mac for a year and two months, but still getting used to it...

Take it to an Apple store. If it's under warranty (as you suggested), you could get it repaired under warranty. I'm not suggesting that you lie ... but if they don't ask you if you spilled water on it - you may not need to tell them.