A couple of comments I haven't seen yet in this thread, based on my own experience getting back into cycling after 20+ years away (and I was never a racer).
If you haven't already, get a medical checkup, including treadmill test. This will clear you for action as well as give a baseline for future testing. (I started riding without testing, but after a particularly arduous and hilly ride, friends convinced me to get tested ASAP.)
As Hermes pointed out, you still have neuro pathways and/or muscle memory that can be rekindled. But watch out for the mental part: I found it extremely frustrating mentally to fall far short of what I used to be capable of doing. Focus on training based on your current conditioning, let go of any expectations based on the past, and especially just enjoy yourself at whatever level you're at now. Retraining and reconditioning is a slow process (at least it was for me) so when I finally relaxed and decided to train based on my current condition, not my past achievements, it was a breakthrough. Sounds like you may realize that already, just wanted to add my 2¢.