I'll chime in here since I'm currently on week 7 of recovering from pretty much the same procedure. Open heart, triple bypass so not quite exactly the same, but they still cracked me open like a lobster. I don't want to scare you and I'll preface it by saying mine was definitely NOT the typical experience, due to constant mistakes on the hospital's part, but it was hands down the worst thing I've ever gone through. I've got a pretty damn high pain tolerance and I always say that I want to live forever, but if you had handed me a gun in the first 24 hours after the surgery, I would have swallowed a bullet. That was their first screwup-forgetting to give me any sort of painkillers after the surgery so we were chasing the pain, and being Irish I have damn near immunity to painkillers so nothing helped until day 2 they finally said fuck it and loaded me up with fentanyl. Second mistake was they forgot to turn on the pump connected to the three tubes jammed into my chest to pump the bile out of my stomach, so I blew up like a balloon. Then they kicked me out of the ICU way too early since the surgeon wanted another bed so he could do another one and I was the youngest (44) and "healthiest" patient they had. Your guy's name wouldn't happen to be Caldeira by any chance is it? Sounds same as mine, does a couple hundred a year, giant ego, and a real asshole to boot. I'll skip the rest of the gorey details, but the cliff notes version is I coded twice, had to be brought back, bounced back and forth from the ICU 4 different times, and ended up being in there almost two weeks.
Oh but the fun didn't stop there. On my way to my 6 week followup I started sweating like a whore in church, went blind, and started vomiting like the exorcist on steroids. We pulled over and called 911 and when they got there my BP had tanked to 70/30. They took me to a real hospital and turned out the shitty hospital where I had the surgery let me leave with pneumonia, sepsis, and a blood clot that had gotten into my lung so I ended up in there for another 4 days and now I'm on two different major blood thinners for the next 6 months. Again, not trying to scare anyone, but the nurses all used the same line on me - "80 year old ladies get this done all the time, you'll be fine!" Just by coincidence, my 50 year old cousin went in for the same procedure about 5 days after I did, and he had the standard experience. A lot of initial pain, but out in 5 days, pretty close to being recovered now. I will say now that the pneumonia and blood clot are gone, I feel a hell of a lot better than I did, and am starting to get back to normal life. You will definitely feel much stronger and have much more stamina afterward, so overall it was worth it for me, but definitely not something I would ever want to go through again.
Couple quick things they don't tell you about. First, and definitely most important, if you don't have one already buy yourself a bidet or a bidet attachment for your toilet. You can get a decent one off of Amazon for like 30 bucks and they install in ten minutes. Seriously, life saver. Second, it's truly shocking how quickly you lose muscle mass when you're just sitting on your ass in a recliner 23 hours a day. Third, it will definitely take a mental toll on you. I'm a generally upbeat guy but having to rely on someone else for the most basic of tasks and the feeling of complete helplessness and uselessness eats away at you pretty quickly. Lastly, definitely do the walking, the breathing exercises, and the cardiac rehab. They help immensely and just seeing yourself make progress even if it's small helps with the mental aspect.
TL;DR version- It fucking sucks worse than anything that has ever sucked, but overall it's worth it in the long run. Any other questions, feel free to ask.
Good luck, hope everything goes smoothly for you!