I've been writing a lot more words in Spanish lately as I gear up for giving lessons in Spanish so I (well really, Greg) recently figured out how to use accents and punctuation elements in Spanish, which has made my life much easier!
Go to System Preferences, click International and then choose US-Extended. Once you're set up with that, the keyboard shortcuts are as follows:
option+e+vowel = accented vowel (lower case)
option+e+shift+vowel = accented vowel (upper case)
option+1 = upside down exclamation ¡
option+shift+? = upside down question ¿
option+n+letter = tilde over letter ñ
You can also experiment by holding down option and pressing random keys.
¡Allí está, suerte!