Oh! what a beautiful dog!
One of the best dogs I ever had was a semi-retired finished champion intact male (the breeder was still using him for breeding, but wanted him in a home, not a kennel). I think he marked all of twice and both times were my fault. When you get your new guy, work with him like you would a brand new puppy. Crate-train (I am sure he already is, but reinforce it). Tether him to you so he can't get a chance to sneak over somewhere and mark something. Take him outside regularly to the approved spot and praise, praise, and praise some more for appropriate eliminating. Don't let him have free run of the house until you're positive he knows what to do and where. This could take weeks to months, depending on the dog. Terriers are a bit more strong-willed than my herding dogs, so it may take a little longer than it did Striker, but he can and will learn with close supervision and proper guidance from you.
This is exciting, I can't wait to 'meet' your new little guy! Don't forget to post pictures.
Best wishes!