"How was Surveyor-3's location known to such accuracy?"
The Surveyors were located using Lunar Orbiter photography (not necessarily of the probe themselves, just the surrounding area).
These coordinates were obtained by determining the position of the
landed Surveyors on Lunar Orbiter photographs by matching features
shown in Surveyor pictures ...
(This answer doesn't directly address the question, but it dovetails well with Organic Marble's on-topic answer.)
On the landing approach, Conrad saw and identified "Surveyor crater" very quickly after the "pitchover" maneuver that allowed a surface view out the windows of the LM. This was a 400-foot wide crater inside which Surveyor III ...
The Apollo 12 Preliminary Science Report contains a section on Surveyor 3.
Among other findings:
no evidence of "cold welding" of the parts.
dust kicked up during the landing of the Apollo 12 LM pitted and "sandblasted" one side of Surveyor
micrometeoroid pitting was light and confirmed the estimates used in designing the Apollo spacecraft to withstand ...
To be precise, the astronaut is posing for a "tourist picture", rather than examining Surveyor.
This is photo AS12-48-7136 (very similar to -7135, but distinguishable by the position of the Réseau marks), with some contrast changes. According to the Apollo 12 image library, there was some back and forth of cameras and magazines because of a mechanical ...
It's the soil sampling arm and scoop.
This Surveyor mission was the first one that carried a surface-soil
sampling-scoop, which can be seen on its extendable arm in the
pictures. This mechanism was mounted on an electric-motor-driven arm
and was used to dig four trenches in the lunar soil. These trenches
were up to seven inches (18 centimeters) ...
No color photographs were taken.
According to Analysis of Surveyor 3 material and photographs
returned by Apollo 12, p. 3,
During their second EVA, astronauts Charles Conrad and Alan Bean reached Surveyor 3 on November 20, 1969, at 06:27 GMT. They spent about 25 minutes at Surveyor and an additional 10 minutes at a nearby small crater ("Blocky Crater"), ...
The Lunar coordinates of the landing site were 3.01239° S latitude, 23.42157° W longitude which Ewen Adair Whitaker ( who had previously successfully located Surveyor 1 for NASA) designated as 1,180 feet (360 m) from the location of Surveyor 3, a distance that was chosen to eliminate the possibility of lunar dust being kicked up by Intrepid's descent engine ...