You can get Heirloom seeds from MyPatriotSupply.
Their prices are a bit steep. Check out out smaller seed companies that have a non GMO pledge. They sell many heirloom seeds for a fraction of the cost. You have to take into account things like : what do I like to eat? It's great having seeds for heirloom broccoli if you can't stand the stuff!

Rancher is spot on when he says try raised beds, they are much easier to manage and protect. My neighbor has had great success with straw bale gardening, this too, is very simple with the added benefit of supplying broken down compost at the end of the season.
As mentioned, your local library will be a great source of info about many of the questions you have, attack it one item at a time.
