I believe that you have the VG30 engine, if this is true you have to remove all of the belts and to do that you must find all of the adjuster screws for the accessories that are attached to the appropiate belts and lossen the pivot bolts. once all other belts are removed you can begin replacing. my advice is to replace all the belts while you are there and save your self from the hassle of this again.
If the motor has not been turned over without the belt you should be able to put the new belt on where it is..
Timing belt
The recommended mileage to change a timing belt on a 1995 Nissan Pathfinder is 100,000 miles. The belt may need replaced before this.
Timing chain
Chain
The 2001 Nissan Pathfinder has a 3.5 liter engine with a timing chain rather than a belt. http://www.samarins.com/reviews/pathfinder.html
The alternator belt on a 1993 Nissan 300ZX will typically squeal if it has excessive wear or it has become lose. This provides a good opportunity to replace the belt before it complete fails.
Timing chain
105000 milesd
http://wiki.answers.com/Q/Does_1999_nissan_pathfinder_have_timing_belt"
Yes
hyow much play on the belt do you have. and also if there is any cracking of the belt replace now.