all looms ona sierra are sperate like

electric mirriors
central locking
electric windows
abs
heated screen

most late sierras have the plugs built into the loom, so alls you have to do is get the proper loom plug it all up and away you go

most tat have electric windows have electric mirrors aswell, so door looms are a must, will be a black plug inside doors for electric mirrors

the connectors for looms will be behind dash so dashbaord will need to be removed to install everything but its easy to take out anyhow