First timer

Im 44 years old and have signed up for the St. Anthony's Olympic triathlon in October. (Usually it's in April but was moved due to covid). It could be the smartest thing I've ever done or the dumbest. The jury is still out. You see, I had shoulder back in October of last year where the doctor fixed the tears in my rotator cuff and labrum. He also took out numerous bone spurs and relocated my bicep tendon (biceps tendonesis). The bicep tendon ended up snapping about a month after surgery which caused my bicep to relocate lower on my arm towards my elbow. If that was everything I still would think Id be ok to do a race but it gets better. My shoulder has bone on bone arthritis from playing professional baseball for 10 years. During a follow up appt. with my doc I asked if I'd ever be able to work out again and he laughed. I then asked him if It would be possible to do a triathlon by the end of the year and he said no. This is no slouch of a doctor either, he's actually the team doctor for a major hockey team who won the Stanley Cup last year but I won't say which team. So despite the fact he said no I signed up anyway. Now about 9 years ago I snapped my patellar tendon dunking a basketball which caused my knee cap to retract up into my thigh and before that I've had 2 back surgeries. Add in a reconstructed elbow surgery (Tommy John) in 2000 I'd say my medical chart is quite extensive. Currently I have been swimming which is the only discipline I really care about considering my shoulder. My swimming has gotten better and the pain is always there but it's manageable. I've done some 500m swims and Im going to push that to a 1000m come June. That will give me 4 months of training to get to the 1500m mark and I will get there. The other day I did 20mi on the bike with no problem from my knee at all. Running is a bit difficult to because of my back but I have done a couple 5k's and made it to the 4mi mark 2 days ago. I want so badly to prove my doctor wrong but at the same time, do it for myself.