Does anyone have advice on how to plan a back yard into a garden?

[mopinko]

5. how is your soil?

srsly, i would spend the first year just working on the soil, unless you know it is good. get it tested.

at any rate, i have found wood chips are a great, quick, all around soil builder. if you lay a thick layer down while it is still winter, if you can.
about 50% of it will rot down within one season, and the rest will hold water pretty well.
even if you dont till them in, the worms will come and do it for you.

a peach tree is a pretty good choice. but a lot of fruit trees these days come in semi-dwarf. there are lots of "two-way" trees out there, too. more than one variety on one trunk. or even more.
my "trophy tree" is a 4-way, espalier asian pear. best part is they ripen at slightly different times, so you have them for several weeks.

have a 5 way apple, too, but just planted it this year.

just make sure you clear out a big enough hole to have nice, good, loose soil around it. lots to say about tree planting. read up.
the first fruit tree i planted i did in a hurry. we had just bought the house, but came over and planted it while the other people still were here. was nervous and kinda just dug a hole and plunked it in. didnt clean up the roots that were circling the pot. the tree is still alive 30 years later, w almost zero plums. strangled by its own roots.