Having problems now with this 2000 Chevy Silverado..

Hi, there. So I just purchased a 2000 Chevy Silverado 1500 5.3L v8 auto. The truck is not like perfect but more like a winter vehicle for me. I'm having some issues with it now, truck ran good and started with no issues , but at the same time it came with ABS , BRAKE LIGHT, SERVICE ENG LIGHT and the one that kind of bother me was the SECURITY LIGHT on dash , sometimes it stays on and sometimes goes off and on , but still truck was running fine. Now this is the problem I'm having now , I put the OBD code reader and it's telling me the ( bank 2 sensor 2 that there is no activity ) , this thing has a bunch of sensors , or tho I think I know witch one it is , perhaps the one sensor that's after the cat-converter on passenger side if I'm correct , now the code reads: ( P0160 o2 sensor Circuit No activity B252 ). Now it does has an exhaust leak on the muffler on that side so that could be one issue why the truck it's starting to do what I'm going to explain ahead. So the truck a few days ago started like acting like it won't want to shift. Like the engine revolutions are up but like there is no gears grabbing. I never experience anything like it. OK so like say you started it , you into reverse ,I back up fine , shift into D and it goes fine into gear and grabs it , but like once I accelerate you should heard that next gear go and take it , but in this truck is not , u press the gas and it accelerates , revolutions up where they should be but is not wanting to go unless u really really accelerate the truck it will grab gear but its a heavy gear like she was stuck on a low gear. I was also checking about the selenoids , this are inside the transmission , not to hard to get to them for what I see , take the bottom pan out , of course I will replace that transmission filter when or if I do it , and the selenoids should be there visible , just have to unclip them carefully so I don't brake them clips , cause if I do then I'll have to replace wires and I do not feel like messing with it. But anyways I was checking and the o2 sensor could make the truck do some crazy things , but also them selenoids inside the transmission and of course thatRobles with that %#*@ security light been on I'm not even sure about that. All I want is the truck to run and shift right like it was before , I checked the transmission fluid and Its good , I check some fuses good , now I'm not sure about that o2 sensor or the selenoids , I haven't taken them out due to so much mud and rain in and around my area where I live in Ohio , I do have a garage but I'm not about to take my baby out of there to put this peace of crap in there , so I'll wait till at least I could get a good day that's not rain , cause it's been like none stop and on top we did some house work and one of the things we did was correct a water leak in my base,entry so had to basically brake ,y driveway up some to get to do what was done on my home , and the mud now it's so horrible … that I'm been force not to do any type of work here , cause it's just way way way to horrible , so I'm hoping sometime this week I can get on it and see what can be causing this issue. If anyone has experienced the same issue as I have , let me know what they think it can be , that o2 sensor or the selenoid on transmission so I can get this thing running , I just need at least 2 perhaps 3 good winters out of it , it has a good v8 vortex engine no leaks , no smoke or anything , body bahh it's a little rough but still runs like a champ strong , it's just this issue I'm having now with it. Please let me know if anyone has any sugestion or can tell me what could be the cause of it and acting like it is it will help me a lot. Ty and GOD blessings