After my 05 Altima started running a bit rough, I replaced the ignition coils, and it eliminated the problem. It started out as a tiny problem, but it got rougher the longer I kept the old coils on. FYI, I purchased these from O'Reilly's and they were $45 dollars. Of course these are Ignition Coils, so they are all pretty much the same, but I've had them installed for about a week, and so far they've been exceptional!

Unfortunately for the 2005 Altima, the ignition coils are not accessible on the top of the engine because of the engine cover. This is a photo of the engine cover after I removed the bolts. There are a total of 4 12mm bolts. You'll need a socket wrench to get these out. On the plus side these don't have a lot of torque so they just came right off.

This photo was after I removed the engine cover, and started removing the ignition coils. Once you get the engine cover off the coils are accessible because they're located on top of the engine. It's a plus because you don't have to remove anything else to get to them.

There is one bolt for each coil. These are 10mm bolts, and I used a socket to take them off. These don't require any extension, just a shallow socket. If you're replacing all four coils, you'll have to remove a total of 4 bolts.

As shown in this photo, there is a harness on the backside of each coil. I would suggest removing these before pulling the coil out of the hole, because it's extremely difficult to move the coils with these in place. It's a tight area, but there was enough room to get a pair of pliers behind each coil to push in the tab, and pull each harness off.

It was fairly difficult to get the coils to pop out of the spark plug holes, it was almost as if they were stuck on. You have to twist these around quite a bit while pulling them out. I had to use my pliers on a few of them to get them off. Eventually I did get them all out, but it does take a bit of work.
These are the new ignition coils as I put them in place. The good thing is that they went back on essentially the same as they came off. One tip I would give is to put the coils into the spark plug holes and then attach each harness. There was nothing too fancy about this, but you do have to apply a bit of downwards pressure on each coil to get it snug in each hole. Once you put the harness back on, you have to put the screws back on. Next, you just have to put the engine cover back on and you're done. Overall, the replacement took about 40 minutes, but it wasn't too bad.

Altogether, I would give the part and A+! They do exactly what ignition coils are supposed to do. My engine isn't as rough as it used to be so I'm pleased with the purchase. If you're in the market, I would definitely recommend these!