Yeah you're on the right track. 


ATU 300 to steer it, screen like a 2630 w/ AutoTrac and Section Control activations, globe on the roof like a SF3000, and JD rate controller. Plus greenstar ready harnessing on the tractor to power/plug all that stuff together. 

SF1 is better than WAAS and still free so I'd start there. ATU 300 you might as well get new, 2630 w/ AT and SC and SF3000 used, rate controller either new or used.