The high-side hose that tends to go is the short one from the compressor to the condenser. Part number for a 2000 model is 92490-7B411, list price is $83. When mine went I could clearly see where oil had leaked from the point where the metal portion joined the rubber portion and the rubber hose was dark with oil.

Replacing it was a piece of cake, I just released what little pressure was left in the system from the low side line using the Schrader valve near the brake vacuum booster, then did a quick swap of the high side line. The less time the system is open, the better. It's just a couple of bolts.
(Yes, I know, you're not supposed to vent the system to the open atmosphere, but it had done most of the venting on its own already).

The oil is Nissan A/C System Lubricant PAG Type R, part number KLH00–PAGR1, 6.8 oz total in the system. I added one of these just to be safe and replace any missing oil:
http://www.id-usa.com/product.asp?CID=34&PID=108

I did not draw a vacuum on the system when I recharged it, but you really should to remove the air from the system. Mine seems to be running fine though. I added the oil charge can (including 1 oz of R134A), then let it take what it wanted to of the refrigerant cans. It took about almost two 13 oz. cans, which jives with the 21.16-24.69 oz. capacity.
Just get refrigerant only, NOT the kind with the oil and refrigerant together. I don't think I even saw any of the combo type that had the PAG oil in them, they were all ester.

Brent