There will be others who can answer more and in depth, but quickly:
How come the blades on some sticks are white and some black? Tape. Players tape their sticks, and color of tape is a preference.
How thick is the ice and how long does it take to turn an arena floor into ice? I believe it is only about three inches. The ice can be done fairly quickly, usually in a day. Painting logos used to be time consuming but they are mostly decals now. There is a How Its Made on Youtube.
How do the players on the ice know when the coach wants them swapped out with players on the bench? The coach will tell them how long to keep their shifts, but once they are on the ice it is up to the player to get off. The coach can yell at them, but it really is up to the player. They need to know their position, the game, and timing. If you watch, you will see players alert the bench by raising their hand.
As a general rule do goalies make more money than the other players? Not necessarily. I can’t get at salary tracking sites at the moment. A goalie is valuable to the team but so is a scoring forward. In the NHL the salary cap is going to be a factor.
How much does the goalie’s equipment weigh? No idea. Believe it is awkward to move in as much as it is heavy.
Lastly, what’s going on between periods when the nets are removed and there’s work being done on the net “mounts?” I am guessing that you are seeing the peg holes being cleaned out after the zamboni fills them up with water. The goal is held loosely in place with pegs and the ice resurfacing will fill those holes. The holes start to freeze and they have to be cleaned out, usually with a drill.
Player preference, and a lot of the black is hockey tape. There’s no rules about it as far as I know.
Typically, during the season the ice is always there, underneath whatever floor is on top for other uses (like basketball). The ice is only 3/4" thick - Miscellaneous Trivia | NHL.com - NHL Headquarters
Experienced players and lines generally know, since a shift is only 90 seconds or so. The coach or assistant coach may signal via a yell or hand sign, and the players figure out when best to do the actual switch based on puck location and action.
Top salaries are usually for goal scorers. Goalies are important players and there are two in the top 30 paid players in the NHL, but they don’t generally get the biggest salaries. 2024 NHL Rankings
As has been mentioned, they are cleaning out the peg holes. Most ice rinks don’t use the “marsh pegs” that professional rinks use. The overwhelming majority of rinks use traditional pegs that are inserted into the hollow pipe bottom of the goal and slammed into the ice.
W/regard to the color of the tape on the blade, I could understand a preference for black as it might make the puck harder to pick up off the stick. What might be the advantage of white?
Some players that prefer the white tape think that because it’s so close in color to the ice, that opposing goalies will have more difficulty in judging the shot as it comes off their blade. Supposedly it’s more difficult to tell when the stick makes contact with the ice and what the angle of the blade is. There are also some sticks that are white for this same reason.
I’m not sure if any of this actually makes a difference, but once an athlete thinks something gives them an edge…
Actually at many (most ?) amateur rinks, the nets aren’t pegged into the ice at all, but just sit in place. That was true at the three rinks I played in.
Back when I was a season ticket holder for a Division I NCAA hockey team the coach would blow a whistle when he wanted a line change. It didn’t sound like the Ref’s whistle – it was a really brief steady note like a loud pitch pipe. Each team seemed to have a different tone for their whistle so after you learned what to listen for you could tell when each team was about to change their lines.
I have no idea if teams in other leagues do anything similar.