Hello and welcome.
First off, this is not a death sentence, no life span needs to be lost and if you do things the right way then there is no reason your cat can't thrive and lead a normal happy life. Unfortunately, many vets are not quite up to date with the correct treatment of diabetes (can believe I am still saying this after over 15+ years doing this)
Fortunately, your cat picked you and you are smart enough to research things on your own. This disease cannot be treated by vets as they cannot get the correct information to guide you in treatment. Only you can do that.
I would recommend that you use Lantus insulin. It is the least risky and I believe the insulin that has the most success with not only getting cats regulated where the diabetes doesn't do any damage but also has a very high remission rate where the diabetes becomes diet controlled. It is expensive but you can look on craigslist and maybe save 70% on your purchase.
You will need to tell the vet what kind of syringes you need. Tell him you need u-100 3/10thcc 30 or a 31 gauge with half unit markings
Speaking of diet, Most cats get diabetes in the first place because they eat dry food. (steroids also cause diabetes in some cats) Canned foods under 10% carbs. (No gravy sauce types) are best and dry food shouldn't be fed again not only because of the diabetes but for general health as well. There should be a list of canned foods and their carb contents above in Dr Lisa's web site.
www.catinfo.org
Doses usually should start at 1 unit of insulin twice a day 12 hours apart. With Lantus, it is very important to keep the shots as close to 12 hours apart as possible because of the way this particular insulin works.
If your cat is comfortable with traveling then it shouldn't be an issue. Stress can raise the blood glucose significantly and I imagine you will find out soon enough if the traveling affects the blood glucose numbers.
Home testing is the key along with food. It is the only way to know if it is safe to give insulin as well as giving the information needed to treat this disease correctly.
The board can teach you how. You can buy a glucometer lancets and test strips at any pharmacy. Many people use a reli-on meter as it works well enough and the test strips don't cost an arm and a leg.
Hope some of this helps. This is not as hard or scary as it feels like right now. If you test at home, ask advice from people here, there should be no need to run to the vets for things diabetes related. Ask questions as you need to and the combined knowledge of the board usually comes up with some sound advice.
Very best to you and good luck