You are assuming humans only do things out of greed, which implies there was no human progress before the development of capitalism. But people do things because they want to or because they think it's necessary.

1. Jobs would have relative status, but it would be based on people's opinions of the jobs, not how well they paid.

2. The point of socialism is to ensure everyone gets what they need to make good lives, unlike capitalism, which has to keep some people desperate to make them do unpopular jobs cheaply.

3. People would negotiate, just as they do now. Need a garbage collector? Pay someone well enough to do it.

4. Time and negotiation would do it. We are currently in a ridiculous situation with execs, for example: in the 1950s, CEOs made 10 to 15 times what the average worker did. Today they earn hundreds of times more.

5. How do you start a business differently under capitalism?

Brain surgeons tend to be attracted to doing an interesting job that helps people. That would not change. The social status would stay, and there would be sufficient material support to make the job comfortable.