I've changed out about ten sets of struts on varying cars. It really depends on the car. My 2005 Xterra was pretty easy.
My wife's Acura RSX was a little more difficult because of the tighter space, especially the rears. Had to remove interior panels and the top nuts were pretty hard to reach.
If they are MacPherson struts, strut integral part of stearing system, then you will need to have the front end re-aligned once you replace them.
If you have worked on cars before, and if you have a shop manual, factory or Haynes, you should be able to do it yourself, but be willing to give it a full day for all four.
Also, pay attention to how they came off the car. Some cars require all the parts to go back in exactly how they came out, but you don't realize it until you try to put the assembly back on the car and realize the top holes do not line up, even though the bottom does.
You can rent the spring compression tool at AutoZone or O'Reilly. Make sure when you buy the replacement struts that you buy all the wear parts along with the cartrdige, like the rubber bumpers, dust covers, etc. You won't want to reuse the old ones.
Not sure how much the dealer or a repair shop would charge, because I get satisfaction in doing these things myself.
Actually about to replace the wife's Acura TSX shocks/struts all the way around, along with brake pads.