Don't know about the keyboard, but what about installing a small exhaust fan in the same place you had the DVD-ROM using the DVD slot instead of drilling anything?
Something like this for instance:
http://www.ebay.com/itm/CPU-Cooling-Fan-For-Acer-Aspire-5750-5755-5350-5750G-5755G-P5WS0-P5WEO/351690740877
Be aware though that no matter how much air you blow into it or suck out of it, it's temperature will never be bellow room temperature so if you live in a very hot place there's not much you can do about it - been there, done that, trust me…