Lantus is a great insulin. Please check out the lantus/levemir forum and the stickies (posts stuck to the top of the forum) to learn more, that is the forum where most of the lantus users post. You will want to start home testing so you can dose appropriately but that is the same with any insulin. We followed the tight regulation protocol and had Vyktor in remission within a few months. 85% of cats who start following that protocol with lantus within 6 months of dx achieve remission so if you are able to follow that protocol that is what I would recommend. Check out Vyktor's spreadsheet (the link is in my signature at the bottom of this post, click on SS) to see how it worked for us. Don't be put off by how frequently I tested as it's not required that you test that often. The minimum tests that you need to do are the PreShot tests (to make sure it's safe to inject) and one mid-cycle test in each cycle (day and night), preferably at different times for the purpose of putting the jigsaw puzzle of the cycles together and determining dose.
Welcome to the best place you never wanted to be

ask as many questions as you like, we all know how overwhelming and confusing everything is when you first get the diagnosis.
Question for you - what are you feeding Salem? Diabetic cats do best on a low carb diet but I note that if that's not what Salem's currently having you won't want to start changing over until you are testing him as it can make a big difference to the insulin requirements.