I have sewn for many years. Good luck on your first piece. I also would suggest something much simpler than a coat for a first garment. There are alot of sewing techniques that are needed in a garment to make it look nice enough to wear. I have a wonderful book- old but probably still available somewhere that gives alot of specialized instructions that are very helpful. Palmer and Pletsch published a series of books on pants, tailoring, and some other subjects. These books are easy to understand and full of wonderful instructions. Hope this helps.
Cheryl

I wish to add my two cents.

The best thing you could possibly do at this point is get Nancy Zieman's book (and video, if you can afford it) on "Pattern Fitting with Confidence".

You will buy a pattern that is sized completely differently than you think you will need; but the alterations will be so simple that it will be well worth the price.

IMHO

I have made and designed clothing for years. If you want to know if the top will fit, measure all the pieces that go around the bust line. Don't include the seam allowance. The pieces need to add up to about 1-2 inches more than your bust measurement at the fullest part. If you really want the jacket to fit correctly, cut the pieces out of some cheep, old fabric. It doesn't need to even match. Then sew these pieces together using a basting stitch. Adjust and fit until the entire piece is the way you want it to fit. Then, take the trial jacket apart and mark the pieces. Using the pieces, cut your good fabric out and put your jacket together. It doesn't matter what size it is as long as it fits and is the correct length. When you are finished, store your fabric pieces as well as the rest of the pattern in a ziplock bag. You now have a jacket pattern that will always work for you.

If the jacket is lined, don't make practice lining pieces, but do consider there will be another layer of fabric between you and the outside fabric. When you are ready to cut the lining, use your fabric pieces so you get the right fit, adding any extra pleats if needed. If you need more help, PM me and I'll be glad to help. Gwyn