Switching and drive numbers
The gate threshold voltage maximum is 4 V at 17 µA drain current. The datasheet specifies 10 V drive for the rated on-resistance.
The tab is the drain. Mount it on a copper pour on the PCB to pull heat away. Surface-mount orientation is obvious from the tab and beveled corner — no lab bench needed to get it right.
No direct replacement or second source is listed in the official records, but the part is a standard OptiMOS™ 40 V N-channel in a common package, so functionally similar parts from the same series may fit with a layout check.