Congrats on your pregnancy. Similar tale here, 3b tear with DC1 after episiotomy and forceps. I luckily healed pretty well (some faecal urgency but that's about it) but it took about 5 months and a lot of Pilates to get my pelvic floor back to nearly normal.
Even before DC2 was conceived I was adamant that I'd be having an ELCS. However, after having a scan of my scar tissue which confirmed Id healed well. I spent the last trimester of my pregnancy umming and ahhing about whether or not to have a vaginal delivery. My consultant and the colorectal team who scanned me were happy for me to deliver vaginally, on the basis that the risk of tearing again was low.
For me, the advantage of trying for vaginal delivery was that if it went well (and I was regularly told that 2nd births are generally easier) I would potentially be able to leave hospital more quickly and have a shorter recovery than with an ELCS. I think there was also a completely irrational desire to have another crack at a "good" birth?
In the end though, my desire for control over the process won out. My first labour felt fairly chaotic to me and I didn't feel that psychologically I could face that again. I knew that I wouldn't be able to concentrate on breathing, positioning etc if things started to get difficult. I chose an ELCS but agreed with my consultant that if I went into labour before my EDD I'd go with the flow and try vaginal delivery, on the basis that if I went into spontaneous labour I would have already lost that element of control. I had an ELCS at 40+4, though had I not been willing to try vaginal delivery at all I think they would have delivered at 39 weeks. The ELCS procedure was the complete opposite of my first delivery: calm, controlled, and I was able to spend time with my baby straight away (was taken into 1.5hrs of surgery almost immediately after DC1). My recovery was straightforward (up within 24hrs, off painkillers completely within 10 days) though I did need a fair amount of support at home in the first few weeks, mainly for lifting my toddler! There are loads of threads on here about recovering from ELCS which I found really helpful when deciding.
I was lucky in that I felt very supported in my decision making process by my consultant. Previous 3rd degree tear is one of the medical criteria for ELCS in my NHS trust (and the NICE guidelines I think), and while they were happy for me to deliver vaginally I never felt under pressure to do so. I was also lucky to have access to an excellent integrated gynae/colorectal team for scanning and assessing how well I had healed, as I felt I had the information to make an informed decision. Might be worth asking for similar if it is not routinely offered by your trust? Before the scanning etc, I was advised that if they found significant issues remaining from my first labour which required surgical correction, they would advise delivering vaginally then fix it all in one go afterwards, rather than having to have a surgical delivery then more surgery later, with two recoveries. If you feel that you've not healed well this might be something to think about.
Hope this makes sense, aforementioned DC2 is currently snoozing on my chest!