Dirty30

My 16 Yukon (126K )is having hard shifts in low gears and some stalling from P-1st. Ive been doing a little research on trying to fix myself and was wondering if most the issues come from TC and/or valve body? Would it be wise to replace TC, Valve body, & wire harness without pulling gears and such? Or even just try new valve body and do it with Trans in vehicle? Id feel comfortable doing that work, beside tuning new valve body to computer. I could have dealer do that.. Just curious of others opinions? Its my wifes daily driver no towing, fluid changed around 50k, w/ latest change w/ Mobile 1 recommend fluid, so id hope internals would still be good? Trying to be without a vehicle as little as possible. If I take it in anywhere, where I live im sure they'd have it a couple weeks. Thanks. PS Anyone recommend a certain kit, who to avoid? Have read mixed reviews on Monster Trans..