Good for you, girl, tryna take care of your Aztek and keep her on the road.

You learn as you go so just take each issue with patience and troubleshoot it as the problems come. Over the years you'll start to feel like a mechanic yourself, to a degree. It just takes time. It also helps to know when to fold -- for example, I needed the oil pan gasket redone, and I began reading online schematics and the Chilton manual for my Aztek, and watching YouTube videos to learn what all is involved. I realized it was above my level, definitely something to take her in to the shop for. It's hard to find a mechanic that loves or respects an Aztek, in my limited experience. I'm still looking for a mechanic whose eyes light up when they see my car -- probably will never happen!!! Pretty sure my eyes are the only only lighting up.
My local library has a subscription to access the Chilton autocare manuals online, so I can a log-in to those from my house with my library card through my library's website. You might see if you local library does the same thing, and if they do, ask them to show you where to find it online - because it can be kind of obscure on a library website.
Another recommendation I have, if you can swing it, is to get a AAA membership. In 2018, I had my girl towed 3 times for a recurring issue the shop just couldn't diagnose correctly and fix until the 3rd try. It costs about $80 to $150 per year, depending on which plan you sign up for and how many people in your family you put on your plan. I have the Premier membership which means I can get towed 4 times a year, I think at least 100 miles - I forget. But I have such peace of mind knowing I have the AAA card in my wallet, and it gives me some independence, too. I call AAA first, husband second!

Another nice thing about AAA, is if you need your battery checked or have a "no-start" like you just had, they can come out to your house and do a little testing and see what's up, and then offer a tow if need be. They can jump your car or sell and install a new battery for you on site. I had them come to my house to install a new battery in 2020, and it's STILL good. I had Interstate batteries for multiple years prior, and they always died early, yet the pro-rate would only give me $7 or whatnot. I don't regret switching to AAA for battery.
I can't help you with the starter because I don't have experience but I've worked on other things on my Aztek. When you can't find a good YouTube video on the Aztek specifically, try the Montana mini van. Also, I believe the Grand Prix has the same engine as the Aztek, so that can be a search alternative, as well.
Good luck. I've be happy to help if you ever post about an issue I have experience with. I will say, my husband actually picked out this Aztek for me back in 2009. He saw it was a good deal and ahead of it's time. So he doesn't hate my car but also isn't overjoyed at all the wiring anomalies and such!