Pooks,
Welcome back to the saddle! I am coming up on my first anniversary of taking back my life and health on a Trek NAVIGATOR 50! You can do ALMOST anything your heart desires on your hybrid if you train and really WANT to accomplish it.
I came back to riding at close to 300# last year and in terrible shape. I started riding and haven't looked back. I regularly do metric centuries (over 62 miles) and have just finished my 3rd FULL CENTURY yesterday (8 July). Use your gears! Start in comfortable gearing so that you can continue to spin without tiring yourself. You will get stronger the longer you are able to ride. Build from shorter distances to longer ones. You won't break any speed records like the road bikes, but just KEEP PEDALLING!!!!
If I can do it, nearly ANYONE can! My Navigator currently has 3,788.7 miles on it in less than a year and MOST of those are on the road.
Have fun and to paraphrase Dorey from Finding Nemo... Just keep pedaling, Just keep pedaling...

Mary