1997 Chevrolet Silverado Recently Had Distributor Changed Out Because Hold Down

I recently had my distributor changed out because the hold down on the cap broke and now I have 4 dtc's p0300 random misfire, p0420 x2 catalytic effientcy below threshold, and a p0430 now my truck misses terribly and i lose overdrive when it's cold but after it warms up the miss goes away and regain overdrive. I took a temp reading on both the cats and they are up to spec in that aspect next is a back pressure test. Wondering if this is due to bad o2 sensors or what I don't understand why the problem improves after its warm?! HELP