No need to go with 700c wheels as long as your current 27's are in good shape. This is where I would begin.......

1) new tires and tubes

2) fenders (700c fenders work with 27" wheels) I don't run fenders at the moment.

3) rear and front racks

4) Bar and seat bags (I like Connondales)

5) battery operated handle bar light for starters, and a tail light (flashing red)