Returning after 2 1/2 years, IM Texas?

I have just started back after a 2 1/2 year break. Prior to the break I had several years of training under my belt, 4 full IM’s, several halfs, some 50k and 50 mile runs. I might have “accidentally” signed up for IM Texas. The first week and half back shows me how bad a shape I am in, run is slow and bike power is really low. I am in terrible shape and need to drop about 15 lbs.
This puts me about 38 weeks out. What are your experiences after a long break? How quickly did you build your base back? With consistent training do you think I have enough time?

Best,
E