HEL is a very nice destination, hotels have a very high standard in general... the airport is about 25 min from the center of the city which is situated along the souther coastline of Finland...
The city is very modern with huge shopping centers and it is very easy to get a round since almost everyone is very proficient in English.
You'll find that Finland is one of Europe's most advanced countries in terms of technology and the transportation infrastructure is very well developed.
The airport terminal is L shaped with shopping and eating on the main floor, departure is always from the 2nd floor which is the main and arrival on the 1st floor, this is also where the baggage is picked up. Most aircraft arrive at gates which are numbered from 1-35 with the lower numbers most often used for domestic aircraft.
I am based at HEL flying for Thomas Cook, if there is anything special you'd need help with, you may ask me anytime =)