Installing a garage door opener is not that difficult if you have the right tools. But, I recommend paying a professional. When I say professional I mean an actual garage door dealer, not someone from Lowes or Home Depot. I also recommend buying the garage door opener from the professional, not from a home center. Here are my reasons for these statements:
-You'll have a labor warranty when you hire a professional.
-You'll have a warranty on the parts when you buy it from a professional.
-A professional will usually adjust and lubricate the garage door as part of their installation.
-A professional will use heavy gauge angle iron to hang the opener, not the flimsy straps that come with the openers from the home center.
-A professional door dealer will generally use a garage door opener that has a one piece boom/rail. All openers sold in home centers have either a three or four piece rail.
You can expect a $75-$100 charge for the installation of a garage door opener. Well worth the price for the above mentioned reasons. Fully installed garage door openers (materials & labor) go for $250-$300 in my area.
You asked if it matters if the door is a 2-car door. Well, the answer is yes and no. If the door works easily by hand (manually) then pretty much any garage door opener should work. If the door does not work easily by hand then you may have a problem with the garage door that may damage any garage door opener if the problem isn't taken care of. All garage door openers are meant to work on a properly counterbalanced and adjusted garage door. I see a lot of people that think a garage door opener can take the place of the garage door springs. This is false and dangerous.
If you decide to install a garage door opener yourself, here are some tips that may not be obvious:
-Get an 8 ft. step ladder, or borrow one. You can use the step ladder to prop the opener up until you can attach it to the ceiling.
-If you have a garage door that is not made out of wood, then you may need an additional part that most people call an operator reinforcement kit. It's available from the garage door dealer that put your door in. Some professionals call it a drawbar plate. Some doors will also require a reinforcement strut. Check this out before you plan to install the opener, you may have to make a run for parts.
-Make sure you have an outlet on the ceiling that you can plug the opener in to.
-If you have no way into the garage except through the garage door they you may want to purchase a keyed disconnect device that allows you to disconnect the opener from the door from the OUTSIDE in case of a power failure or if the garage door opener doesn't work.
-If you don't have a garage door opener now, make sure that you have enough room above the door for it to fit. You typically need 2-3 inches above the highest point the door travels above the tracks.
Even if you plan to install the opener yourself you can get a free estimate from a professional dealer first. This would tell you if 1)an opener will fit, 2)you need any additional work on your door.
Professional Door Dealer