Well, by your own admission, you've been "very lax" about maintenance. So, you can't blame Mother Nature for taking-back what was hers...I would suggest starting with a smaller portion of the hillside, and building from there as time and your experience grows. A beginner mistake is to try to tackle too much when one is just starting/learning. I would spray Round-up or Clean Sweep. Wait a few days, then hit the weeds you missed again. Then, plant a smaller area with perennials that don't require a lot of maintenance (peonies, day lilies, daffodils, all love hillsides). Then spread a good three inches of mulch around the plants as you have seeds in your soil from your "lax" efforts this year...This will greatly reduce the need to weed and water. Add composted soil, if needed (likely), In a year or two, you could perhaps expand if you find the effort worth your time. Otherwise, go back to watching TV. It takes real effort to maintain a decent garden. Not all of us are willing to actually do physical work (note American obesity rates). Or, just write the checks and have someone else do the work for you. (Heavy sigh, here).

Turn it into a rock garden with just a few plants here and there.

GRDNGUY,
If the poster has had this hill for 33 years, I would hardly consider him/her a beginner. Also, those years likely put the poster in an advanced age category. It doesn't seem fair to lump this person in with "lazy Americans" with absolutely no knowledge of their personal situation. If you can't say something nice......

Martha

I like to cut down the saplings and then dab 1/2 roundup and 1/2 water on the cut edges immediately with a foam paintbrush. It doesn't take too many times to get rid of them. I'm fighting bindweed myself, its hard to get rid of. If you take a rake and pull it down before it goes to seed and trace it down to the stump where it comes out of the ground and paint that with the roundup, it really helps. Once it goes to seed, you'll have zillions of seedlings, but if you get them with the rake when they're little it helps. You might have to hire someone to come and do this for you once a month if you're having issues with your health, etc. but it will happen eventually for you. Hang in there!