Hi Susan, Congrats on your engagement! I am a wedding photographer and have seen a little of everything. Traditionally, the bride's maid & groom's men pay for their own, but I have seen them paid for by the bride and groom plenty of times. It is what you work out with them.
Basically, you will need:
An Officiant
Ceremony location (chairs if not included)
Ceremony music
Rings
Flowers & throw away flowers
Dress/Tux
Shoes
Garter & throw away garter
Reception venue
Caterer/Table & Chairs if not included
Cake
DJ
Photographer
Cake server
Champagne & Bride/Groom Champagne glasses
Guest champagne glasses
Card cage or basket
Rule of thumb: one drink for each guest per hour
Limo
As for any unexpected expenses, a good contract should spell out exactly what you are getting and if the professional won't do that for you, I would suggest not doing business with them...even if the price seems right. There are good and bad in all professions.
You may want to look online for reviews and credibility. Keep in mind, people are very apt to go online and write something bad and almost never write something nice. My concerns would be more than one complaint of the same thing...ie, one particular venue here takes a deposit and then the day of or before the wedding says the neighbors have complained and they will have to move the wedding to another location that the bride/groom never saw before. I found this venue had about 3 complaints of this and would be concerned of something like that.
Best wishes and enjoy planning your wedding.