It's not nearly as impossible as it looks.
Jack up the car and take off the front passenger tire.
You are going to be under the car. Use appropriate precautions, and invest in good jack stands. Keep the jack under the car too in my opinion.
Take off the plastic shroud under the fender to get access to the belts. Put your thumb on each belt and judge how tight it is. You've got to get about this amount of tension on the new ones. Overtightening will cause bearing wear; undertightening will cause slippage, underperforming a/c compressor & alternator, short belt life too.
Loosen the idler on the front belt by loosening the bolt in the middle of the idler. Rotate the adjuster from above, and loosen the front belt. Then remove the front belt.
To loosen the power steering belt, you have to first loosen the tie-down bolt, which is very near the other, long bolt that actually loosens the belt. As I recall, the tie-down bolt can be accessed from above. The secret for loosening the power steering belt is to rotate the adjusting bolt clockwise, as if you were tightening it. It will take quite a few revolutions to loosen it. You are actually putting pressure on a clamp assembly, so the effect is reversed.
Put on the new p/s belt and tighten it up by going counter-clockwise on the adjusting bolt, then tighten the short tie-down bolt. Then put on the outside belt and tighten from above. When you get the tension right, then tighten the bolt in the center of the idler pulley.
Serpentine belts do not have to be as tight as V belts; overtightening is bad for them and the components. If you're not sure, you can buy a gauge fairly inexpensively.
When I changed mine, I went quite slowly and managed to spend well over 2 hours. I feel that Nissan belts are the best, and recommend that you stick with them for a long service life.
Good luck & don't forget those jack stands.
JM