A plastic primary I don't believe is an issue. Some of the wines I make with fresh fruit i would rather have the plastic bucket. It is easier to put in a jelly bag then add the rest of the ingredients and tie a cheese cloth or towel over the top. I will keep in the primary for 10 to 14 days, squeeze out the bagg and then rack into a glass or betterboy carboy. With juice only I don't see any real benifit. With fruit you will loose volume after removing the fruit so that is why they usually give a 6.5 primary and 5 gallon secondarys.
Headspace is not as big a concern for the first couple weeks. My meads and wines are always just covered with a towel the first 10 days. When racking to the secondary however this is a major concern! Only leave an inch or two of air space under the airlock. You stand the risk of oxidation if you leave much more.
Degassing is the removal of the CO2 from the wine. In the conversion of sugar to alch one of the by-products is CO2. This sometimes becomes suspended in the liquid. A drill attached rod is sold for around $9.00 that you can insert into the carboy and it whips/stirs the wine without adding air. Be careful using these as they can create an instand foam over as the gas is released.
There are no stupid questions, almost . All of use started somewhere and like anything else you get more proficient each time until it is routine.
Carboys, tubing, hydrometer, hydrometer vial, airlock, bung or stopper for the air, and your ingredients are the requirements to get in started. You will need of course some campden, Potassium Metabisulphite (I don't use Sodium Metabisulphite as I don't want any more sodium), some Acid Blend, Tannin, Potassium Sorbate, Yeast Nutrient, maybe some Yeast Energizer, yeast and juice. I like to keep some Pectic enzyme on hand also. This will have you ready to make about any type of wine. I have a few different kinds going so I need some of these ingredients for some but not others.
Later you will need bottles, corks and a corker. look through the posts and you will get a lot of info. There are many smaller items that can assist or make the process easier on you. Try a batch and see!
Good luck on your new journey!