Max, my dashund missed his step over the curb last Saturday, took him to the vet, he gave him three medications for the next 3 to 4 weeks... What do I expect??
Will he need surgery, vet says possible slipped disc.

Possible slipped disc means that he MAY have to have surgery.
But if he responds well to the medication then he may not, it's just a waiting game.
Limit his activity and definitely make sure he does not jump, or walks up stairs, his body needs time to recover and movement is his enemy right now.

Yes and once the doc gives you the OK to resume normal activity, swimming is one of the best activities you can do with him. My dog Max tore ligaments in his leg, he had to have surgery, and we only needed to take him to physiotherapy a few times, because he was swimming. It helps exercise the joint without putting too much pressure on it. Just make sure to limit, as with anything too much can be a bad thing. I am sure your vet will tell you everything you need to know for the healing process.

Your best bet is to listen to you vet. If you are not satisfied with your vet's diagnosis, get a second opinion. But usually your vet knows best, as they have been trained for these types of things. I know it may seem dumb, but good on you for taking your pet to the vet, it was the responsible thing to do... Many people would have ignored the problem, in order to save a few dollars, but you did what was best for your dog.

I don't know enough to give you a diagnosis, but what Shazzy and Aurora Bell are saying sounds right.

*** Cherish your dog everyday, as it could be the last you have with him. Take the precautions to make sure he never has a chance to go near traffic, and love him like your baby.