Jerry, you can use dumbbells instead of a barbell. As far as the step goes, in the weights workouts I have the regular step is used for one legged squats, which you can put your foot on a stool or something (I'm pretty sure you don't have stairs, do you?), or as a weight bench, which you can lay on the floor or use an exercise ball instead.
If the workout calls for a high step (smaller and square) then if you've got a sturdy step stool or something along those lines, perhaps you could use that. I'd watch yourself, though...you're pretty tall, you don't want to hit your ceiling!!