I'll try to address your concerns as they appear above:
1. The idea of giving injections is scary at first but you'll quickly learn how to do it and most kitties are OK with them and/or can be trained with treats to make it easier.
2. It's great that you have wet food to give Zeta. Many people here find prescription food too expensive and feed grocery store brands like Friskies or Fancy Feast (pate only, no sauce or gravy).
3. There will be ups and downs when you start insulin and it can take a while to get to a dose that works well for Zeta. Patience is key! Lantus, Levemir or ProZinc are gentle, slower acting insulins that many of us here use. There are different forums for these.
3. At the needle clinic they'll show you how to inject insulin and - hopefully - how to do a blood glucose test by pricking the edge of an ear to get a drop of blood. Many vets will encourage you to buy a pet specific meter but the test strips for these are $$$$$. Human meters are very popular with many here. The ReliOn models from Walmart seem to be at the top of the list. The strips are much cheaper.
4. There is a diversity of approaches among vets regarding home testing of blood glucose - some don't encourage it (but having a glucose "curve" as it it's called done by them is very expensive; some are much more open-minded about owners being hands on with their cat's care at home. We encourage the latter.
I've only given you an overview because the details of injections, dose finding, glucose testing and ongoing monitoring are elsewhere on this website. SLGS - start low and go slow in your information gathering. SLGS is an acronym for the approach to treatment that's popular here but it also applies to your own learning curve.
The key communication tool we use is a Google docs spreadsheet where you log all of Zeta's insulin doses, blood glucose values and other notes over time. There's a "Sticky" for how to set this up and people available to help if tech isn't your thing. Other members can see your SS and use it to give advice. Meanwhile, if you click on your name in the upper right corner and then on "Signature" in the left menu that appears you can give us details about Zeta such as his age, date of diagnosis, other health problems if any, what he eats, insulin you use, glucose meter you use, etc. This can be edited any time. Have a look at the light grey small text that apears at the end of everyone's comments on any thread to get an idea of what I mean.
I hope this helps.
