The gold standard imaging diagnostic for IVDD is the MRI, which, 10 years ago when my dog Annie had her first episode of IVDD cost upwards of $1500 in my area. That's just for a diagnosis, doesn't do anything to actually fix the problem. It is typically recommended/required for surgery, but if surgery isn't warranted or not an option, I don't know that there's much point in doing it.
My vet did x ray her back at the first episode she had, and it showed multiple calcified disks, but those don't necessarily make a dog symptomatic. The second time she had neck problems, we didn't x ray, and just started her on medication.
Annie's IVDD affected her neck, and the first episode caused her severe general pain and lameness in just 1 front leg, and the second (years later) which didn't seem as painful, but caused more significant neuro signs, stumbling when she walked, etc. The first time I remember thinking she was never going to get better 2 weeks- may as well have been 2 years for how long it felt- into her recovery (still frequently screaming when people tried to pick her up), it took a while before I saw real improvement, but then it was pretty fast and steady. The second time, it was more of a gradual, fluctuating progress back to her normal self. In both cases, I did crate rest for 6-8 weeks, then slowly returned to normal activity, but the first time she was acting "good" after 5 weeks or so, and the second, she was still a little wobbly at that point.
She was on pred/robaxin/tramadol, and I also started her on Adequan maybe 2-3 weeks after her first injury, when she just didn't seem to be recovering quickly. I don't know if it helped, but I figured it probably couldn't hurt, and there are others who've used it for IVDD with apparent success. She did seem to improve pretty steadily after that, but it may have been coincidence. Once her restriction period was up, I started her with swimming in the bathtub, then eased back into other normal activities. The first time, she made a 100% recovery, the second time (at 14 or 15 years old!), she returned to about 95% function. She was good for a while after that, but these days, sometimes has a strange gait in her front legs, though she doesn't seem painful- I suspect probably loss of muscle tone in old age coupled with still some loss of sensation cause her to not really be able to coordinate her feet well at times.
I would keep the vet updated on his condition via phone if they didn't give a specified time to return, and certainly take him back if they recommend or you notice any deterioration in his condition. It seems strange that they only recommended 1 week of restriction if they genuinely believe it is IVDD, and I would ask them if they feel that longer term confinement is warranted. If you have doubts about the way they're handling his treatment and/or he doesn't seem to be improving, you could always ask for a referral to a neuro specialist, this sort of cases are their specialty.
Here are some links that you might find helpful... just make sure you check with his vet prior to changing anything about his treatment plan: http://vetspecialistsofrochester.com...easeInDogs.pdf Dodgerslist: canine back problems, all things IVDD Conservative Treatment: Healing during a disc episode