YES, Manual to Automatic Transmission is 100% possible. You only need complete wiring set and a TCM (Transmission Control Module). You can get a TCM from old parts market (It resembles the ECM having pink color connector). For your information, the Chevrolet Aveo, having the same engine as of Daewoo (offcourse a bit different being MPFI), also came with automatic transmission so the parts wouldn't be of any problem (except the cost ).
OHC is a generic terminology (Over Head Camshaft). The Daewoo's engine (G15SF - TBI, G15MF - MPI) is an OHC engine with Single Over Head Cam (SOHC).