2) What additional stuff might they get me to purchase or pay for that I do not need?
Since you implied that you are in a cash crunch, after getting this immediate problem resolved, then the answer to your question is probably that you should decline (for the moment) anything which is not a safety issue. But do make careful notes about what they advise, and attend to those as soon as you can. If you can, ask for some kind of priority ranking of any other recommended repairs. As Remco mentioned above, the odds are that the noise you hear is from your front (disc) brakes and for now, you may get by with postponing the rears for a month or two, unless they are likely to begin grinding any day.
The grinding noise suggests that you have worn through the brake pads or linings, which are “wear items.” Please be aware that this means your braking is now somewhat diminished as a result, so the sooner you can get this work done, the safer you’ll be. Unfortunately, the grinding itself suggests that you have begun to damage the rotors and may need them replaced, though depending on the circumstances, the shop may be able to have the rotors “turned”, allowing them to be reused - that may save a few bucks.
Something to remember in a year or two: it’s a good idea to have pads checked periodically to know in advance when they are due for replacement before they’ve worn through. Checking disc brakes is easy so many tire shops do that for free or very cheap. Checking drum brakes (if you have them- would be in the rear only) requires more disassembly so is less likely offered as a free service. Rear brakes wear less than the fronts.
If you already have a regular repair shop that you trust, then go there first. This brake work is a routine job so almost any mechanic can do it. If you don’t already have a shop that you use regularly, this may be a good time to start thinking about finding one, or at least begin your search. Simply having a relationship with a shop is valuable, you’ll generally get better treatment when they know you are a regular customer. Any kind of shop, independent or chain or dealer, can be good. I tend to prefer a place where I deal directly with the owner, or if not, then with the mechanic who actually does the work, rather than an office person.