Don't think you can't do it. It is easy usually. And it gets easier the more you do it. It only gets hard again when you get old.
When I was young I helped my Dad with all kinds of stuff. I never became a professional mechanic like him (he worked as a mechanic at a trucking company working on tractor trailor trucks and he worked construction where they repaired their own heavy equipment oftentimes).
I remember when we built our own heavy lift to remove an engine from my Dad's '63 Chevy truck. My Dad did not rebuild the engine himself although he could have. We did not have space in our garage and he would have had to rent special tools. But we removed the engine. I removed rusty old mufflers, helped my Dad work on brakes, helped remove automatic transmissions with makeshift tools, rebuilt carbs (the old Stromberg was easy to rebuild with just a cheap 'Zip Kit.'). I did all kinds of stuff. We did not try to do everything since we had limited space and some jobs require special tools which you have to rent. My Dad certainly had the knowledge to do everything, especially with the cars and trucks back in those days.
You are probably not going to have to go that far. Just general maintenance with a few simply tools. A lot of stuff lasts longer nowadays-stainless steel mufflers usually last the life of the vehicle. Do what you can with your simple tools and with the knowledge that you have. You will still save money and feel really good. You will find out about tight engine compartments and watch out for hot parts!
There are some easy reading books available intended for people just starting out with auto repair that you can get. Just work safe. You CAN do it. And once you get used to it you will laugh when you remember how worried you were when you started out.
I remember how scared I was with computers at first. When I grew up computers were hugh machines in the basements of universities. Since that time I use computers all the time, and I have even installed my own memory and installed hard drives and replaced and installed other components.
You just have to learn how to do stuff and then go out and do it.