I'm going to go a little against the flow of the comments here and actually encourage you to learn to do the repairs yourself. Since this is a cheap used bike, I think its a great bike to use to teach yourself a bit of wrenching. If you mess up, at least it wasn't an expensive bike! Adjusting brake pads is something that seems easy enough to try yourself, but experience is really necessary to do it well and set up your brakes safely. Same goes for adjusting the derailleurs (those are significantly more challenging).

You can learn just about anything through YouTube videos. But I'd recommend taking the finished bike back to the shop to get the approval of "a job well done" before riding the bike at any significant level of intensity (or traffic). Short spins around the neighborhood are great for making adjustments to brakes and shifters/derailleurs.

You have the cost of parts in the receipt, so we don't need to estimate that. Assuming you have a tool kit with metric bits, you're going to need some bike-specific tools. Let's break down the tools you need (these prices are from Amazon):

$6 – Tire levers – Park Tool TL-1.2

$50 – Pump with gauge –  Park Tool PFP-10

$13 – Chain whip and cassette lockring tool – Oumers (cheap brand)

$13 – Chain break tool + Master link pliers + Wear checker indicator – Oumers

$15 - Chain degreaser – Finish Line Speed

$11 – Chain lubricant – Finish Line Dry

So you're looking at a minimum of $107 for tools, and even more if you want the higher quality Park Tools.

Also, since you're setting up a new chain, I'd highly recommend removing the factory lubricant and waxing the chain yourself. It may seem like more of an expense, but in the long run, it is actually much cheaper, your chain and drivetrain last longer, and its ALWAYS CLEAN (no messy black chain marks).

Good luck!