If I prepare my veggie garden this Fall with topsoil and peat moss will I still have to till it in the Spring?
Not necessarily. If you lay out your rows for spring planting in the fall, it could be set to go w/o tilling in the spring.
I'd give a second thought to the peat moss, though. It can cause a lot of problems. As can purchased topsoil.
Neither top soil nor peat moss are going to provide much in the way of nutrients. I would opt for compost and/or composted manure instead.