Differences between spaniard spanish and PR one are accent and some local expressions. On the other hand, I've read some PR text and it seems to be very similar in structure.
If you understand spoken spaniard you can understand any spanish. Except spanglish, of course. It isn't spanish at all.
About how to write "Ñ/ñ", "ÁÉÍÓÚáéíóú", "¡" and "¿"... my keyboard is different from yours, as JRod said. It has "Ñ" key where your keyboard have ";" one (at the right-side of the "L"). Nevertheless, you can get them typing ALT+[its ascii code]. Ascii codes are in
http://www.asciicode.com. So, if you open Windows notepad and press ALT+164 a "ñ" will be written.
See you!