Can't help you on everything here, but I can help you on a couple things....
You decide whether you want the Tesla Wall Connector (capable of 80 amps of long term charging) or just a 50 amp outlet that is cheaper to purchase, less effective for charging fast, useable for other things besides charging a Tesla, less weather resistant, and less attractive. You've picked the Tesla Wall Connector.
You go to Tesla's website, order one for $550, and have it shipped to you.
While you wait, you have an electrician come out and give you an estimate to install it. Good idea to go with Tesla's recommended electricians as they had some level of training and experience with this. You advise the electrician whether you really want the 100 amp service or just a 50 amp service. The electrician will tell you whether your box can deliver the requested amperage, and what it will cost to run a line to the place you intend to have your wall connector. Proper 100 amp line (2 gauge) is more expensive than proper 50 amp line (6 gauge). There is no standard price for running the line and installing the wall connector; it's just too individual to the site. Total installation cost me $1,600 plus the wall connector. Also, 100 amp service in many area requires an unattractive on/of switch be mounted very near the wall connector. The 50 amp service is unlikely to need that.
Conceivably, you want to get an estimate for the different possibilities, as you might decide to back out of the 100 amp or the wall connector before you buy the wall connector from Tesla for $550, but I was "all in" and bought the connector first. The electrician supplied everything else.
Hope that helps.