The triple uses pylon mounted bootstrap hoists as most other engines do. Only issue with these larger bypass engines is that the propulsor and fan sections have to be separated to ship them. This then gives the engineers a bit more work to do in reassembly.
With regards to the environmental conditions, any airline worth their salt will have a portable engine change tent that will be packed up along with all the other engine change gear. A few heaters and lights rigged up and it will be no worse than changing an engine in a cold hangar in the winter. Well, as long as they keep the doors firmly shut that is.