There is (for each model year) a "LEAF Dismantling Guide" that gives good safety information and perhaps much of the info you seek. I scanned the 2013 version and found a section entitled "P (Park) Position Release Procedure".
This manual (and others) can be found on the following website: http://www.nissan-techinfo.com" onclick="window.open(this.href);return false; That manual also had the following:
Nissan EV Customer Support: 1-877-664-2738 (US)
(Monday-Friday 7am-7pm, Saturday 8am-4:30pm Central Time)
or
Nissan Consumer Affairs: 1-800-647-7261 (US) or 1-800-387-0122 (Canada)
(Monday-Friday 8am-5pm Eastern, Central and Pacific Time Zones)
[Edit Update: I decided to post the above procedure from 2013 DG:
4-2 P (Park) Position Release Procedure
If you need to release the vehicle from the P (Park) position, proceed as follows. When power switch is turned OFF or 12V battery is low, LEAF automatically shifts to P position.
NOTE:
This procedure requires two (2) people.
1. To start the EV system with a booster battery, refer to 4. Jump Starting.
2. Turn power switch ON by pushing the power switch 2 times without pressing brake pedal.
3. Confirm parking brake is applied.
4. Close all doors and press and hold the brake pedal.
5. Place the selector lever in the N (Neutral) position.
6. Remove the following 2 fuses:
• F/L 40A PBW MTR (under hood fuse and relay box)
• METER 1 10A (in the cabin fuse box)
NOTE:
Insert a screwdriver wrapped with a protective cloth (A) into the slit (1). Pull to remove the fuse
box cover (2). Remove the fuse with the fuse puller (3).
7. Release the parking brake.
8. Turn the power switch OFF.
9. Release brake pedal.
Be sure to firmly position wheel chocks when P (Park) position is manually released.
4-2.1 Reset Procedure
1. Install the 2 fuses removed previously.
2. Turn the power switch ON and wait 5 seconds without pressing the brake pedal. Ensure selector
lever is in the N (neutral) position.
3. If 12V battery is low voltage, please charge with battery charger.
4. Turn the power switch OFF and wait 5 seconds.
There were illustrations of fuse box, etc intermixed that I did not attempt to reproduce here.]