I STRONGLY recommend reading Jeff Galloway's training book.
I have used his run/walk break method for years and usually run just over a 9 min. mile. Have done full and halves using it also.
I run a mile and then walk for a min. There are people that qualify for the NYC and Boston marathon using his method. You give your body just that quick minute, or two to recover and you will NOT hit the running wall.
Good job on the starting slow. And about the running shoes--there is A LOT of info out there about shoes that have too much support, spring, etc. and do harm to our ankles, knees, hips, etc.
I wear the Nike Free 3.0 which is supposed to be 'close' to barefoot running--which is how we are made to run! Pick up the book Born to Run for a bit of history on this. Great read.