I was looking into the Nissan service manual for the quantity, but there is no info about it. Here what the manual says:
The 2003 Murano has the all new Xtronic (CVT) transmission.
The Xtronic (CVT) transmission requires a special Nissan CVT NS-2 transmission fluid.
This is the only authorized fluid. It must be used for all service and/or repairs.
Use of any other automatic transmission fluid (such as Nissan Matic D or J) will cause deterioration in driveability and transmission durability.
I'll check some more sources and see if I can find the quantity also, but you can add fluid through the dipstick and see when it reaches the correct level.
Zee