Complex sentence: This was converted into a hotel in 1862, and replaced by "the old stone hotel" in 1879, which remains extant and is used as an administration building by the united world college.
Split into simpler sentences: This was converted into a hotel in 1862, and replaced by a stone building called "the old stone hotel" in 1879. This building remains extant and is used as an administration building by the united world college.