The instruction set = instruction set of standard 8051 (except the instructions timing).
Schematics for simple application = schematics of simple application of standard 8031 (ROM-less 8051, needs external ROM).
Manual can be easily found at Dallas Semiconductor website, **broken link removed** (will redirect to Maxim, but it's OK as they merged a couple of years ago).
It is a pin-compatible drop-in replacement for 8051, just faster.