Just to confirm it's difficult to access, but possible? If so I'd leave it as is and get any leaks sorted out.
I did a bunch of work on my AC system four years ago and haven't had to add any refrigerant since (still blows ice cold). Once yours is dialed in you shouldn't need to access it very...
Installing a car seat in the 80 wasn't an issue for me. In fact my little one came home from the hospital in our 80 after she was born. I'm on the 3rd car seat now that she's 4 and this one should last a while.
If the choice is between a early 80 series (91-92) or a 100 series I'd definitely go...
Part of my decision not to go bigger than a 1.75" lift and 285/75/16 tires is the fact that I can still fit it in the garage.
I worry very little about my cruiser when its in my locked garage (most of the time). Its when I'm parking on city streets that I worry the most.