Hi, I'm in my early 40s, had various symptoms due to low T, went on TRT through a telehealth clinic a couple years ago, and went to the "dark side" about 8 months back. My thoughts:
1) Get initial labwork done. Not just total and free T, but also E2, SHBG, LH, TSH, prolactin, DHT, CMP-14, lipid panel, CBC, A1C, b12, D3, ferritin, and probably some others I can't remember off the top of my head
2) based on above, are you low-T? For the sake of the rest of my reply, let's assume yes, and other causes of symptoms are ruled out.
3) Begin a reasonable TRT regimen, say 150 mg/wk test cyp, split twice a week. Follow for 6-8 weeks, get more labwork, and adjust as-needed based on labwork and how you feel. It's possible you may need an AI, or maybe not. If you feel great without it, then don't use it! If you need it so be it, take the minimal AI dose to control high estrogen symptoms so you feel great.
4) Once you get dialed in, now consider letting it rip. 500 mg/wk of test is considered a generic "beginner cycle"; you'll most likely need an AI so definitely have it on hand. You mentioned prior injuries, so I'd guess your joints probably feel shitty. Deca can help. Around 100 mg/wk is considered a therapeutic dose, just enough to make the joints feel good. Guys report anywhere from 50-150 mg/wk should be adequate for that purpose. I did 100 mg/wk deca through my clinic for several months before my "blast-off" and it makes my joints feel good.
5) Other fun stuff to consider: Primo is considered one of the safest AAS out there, with mild side effects, and it reportedly has AI-like properties of lowering E2. I don't have experience with primo so I'll stop here.
6) Do cardio. It's good for you and can help manage high hematocrit symptoms, if they develop. I like bike riding and running up stairs.
7) based on my experience, the steroids don't do the work-you have to eat, eat, eat to grow. I have a terrible time doing that and am on the cusp of switching gears to get lean instead since I don't feel great with high BF and a constantly-stuffed stomach. But eh, sounds like you'll be fine there based on your previous lifting experience