Yes they are great at what they do. I have a comp 1 in one truck from Firepunk. But I will say I just rebuilt the 48 in my other truck and it was so simple. I psyched myself out for years about how difficult it was. It's all self explanatory once you start pulling it apart. Having the ATSG book is nice too. I can definitely see how it would become muscle memory after just a few times. If you haven't done one yet I would highly recommend it to anyone. It's a cool experience!
I think the towmaster is around 3800 for a 48. The 518 should actually be a bit cheaper because of the converter not being lockup. I bet you could be out the door installed for a bit over 4k.
Well yes of course but you would prob need to use the rh as the re is electronic OD. I suppose you could wire up a switch for OD and LU. I have never driven a 518 but with a super tight converter I bet you wouldn't need lockup especially in something with 160 crank hp.