It's not a perfect fit. The non-AC one is only a 4-rib belt. I ran that for a while when my AC compressor was making funny noises but it eventually shredded and snapped. It's a little to large oddly enough. The non-AC cars use different pullies than the AC cars. I found another AC compressor and got another stock belt so I wouldn't have to worry about it any more.
Correct, a 4-rib belt for a Sentra W/O AC will work. If the parts place has the trim models listed then just go with the Sentra E model's belt. You can also double-check by seeing that the part number has a "k4" in it somewhere (non-Nissan made).
I've read the Nissan part is 11920-77A00, may be superseded since then.
When you place the belt on, make sure the belt is perfectly flush to one side of the pulleys.