You do not need to open the outlet to gather useful information. The pattern of the problem can help distinguish a local receptacle issue from a wider circuit problem.
One outlet is dead
The issue may be local to that receptacle or connection, but a switch or upstream protection device can also affect it.
Several outlets are dead
Multiple receptacles can share a breaker, GFCI, junction, or branch-circuit connection.
Power comes and goes
Intermittent behavior deserves evaluation because a loose or failing connection can be difficult to see from the outside.
Plug feels loose
A worn receptacle can lose its grip on the plug, but the existing circuit still needs to support any replacement.
Warmth, odor, discoloration
Stop using the receptacle. These are warning signs that should not be treated as a normal device-swap project.
Breaker or GFCI trips
The outlet may be only one part of a protection or branch-circuit problem.