I think it was "buffalobill" who stated:

yes because the previous homeowner ran another circuit wire nearby
which is still live. with the level of expertise being low, then
increase the safety level by turning off the MAIN breaker. electricians
have helpers with cellphones and flashlight; they know how to keep
water from coming in thru the wall around the fixture, know what
adapter plate and stainless steel screws to choose, how to select a
photo-eye fixture for your job, how to measure for the hot voltage on
one of the wires to go to the center light bulb terminal of the light
socket, and whether to recommend a GFI outlet nearby for your
convenience in the backyard. they can recommend wiring repairs and
updates to you and give you written estimates for them.

What is THAT all about?? The OP asked about swapping a spot light with
a broken casing . . . .

--
"Trust me, there is NO way to nonchalantly conceal the fact that you have a
power tool in your head, no matter what you do." -- El Gato