you dont have to replace last years soil. You will have to amend it somehow, and replace the nutrients from what you lost last year. If you already have compost I would begin working that into the soil now. If you don't, begin making it now. You can start really easy by adding your coffee grounds (if you drink coffee) to the soil, this will add some nitrogen and other things to the soil that have been taken up by your plants. Don't put the same plants in the same place though. That will definitely invite some mean things to grow and really annihilate your yields. Thats just a general practice.
If you are on instagram follow my guy @marco_is_growing He shows a lot of different ways to make your own fertilizer.
When you say what else is easy to grow from seeds, what do you mean by easy? Are you looking for substantial yields from seeds? You like to grow cucumbers, so you can grow squash really easily from seeds. @DrBanneker is right, okra grows really well. It really depends on what you want to eat this year. There are a lot of varieties for a lot of seeds and you just have to choose. For example, you could branch out and grow squash, and pumpkins also, since they both grow the same as cucumbers. Just don't plant them in the same area. If you can get a sweet potato I would definitely recommend those, especially if you have ones that you forgot about. I grew some that I bought at a local organic grocery store that had sent out all those slips, when they started growing leavs. Technically, each one of those slips can make a new sweet potato colony, but I just planted the whole potato. It worked out really well. I haven't tried regular potatoes yet, maybe next year.
Quinoa is really really easy to grow and so is it's cousin, Lambs Quarters. It probably grows wild as a weed around you. You can eat the leaves from the lambsquarters also, they are very good for you.
If you like them tomatillos also grow very very well and will serve as a nice trap crop for your tomatoes.
Growing sweet corn is like that, but growing flour corn make way more ears per stalk. Corn is pretty easy to grow as long as it doesn't get corn smut, that really can kill everything. As long as you catch it early it will be fine. The biggest thing is preventing other things from eating it, like birds and mice/rats. Scarecrows. If you do plant corn make sure to plant some beans and some squash or cucumbers to fulfill the 3sisters schema.
almost time 
I have no knowledge. I grew a cucumber in my window once when i was little. And we had a school project where they 'gave' us a little plot of land but i don't recall doing shyt. I mostly chatted with the old wm groundskeeper while he did shyt. 
). The next big order will be supplies for the mesh cage(s?) and i still got a lot of seeds on the way. I'll take pics as we get set up. I i should be germinating rn but, in the age of corona, i like to disinfect and then let things sit by the front door for a few days. 
