The blog post at gtamodmafia.com provides a "full mod" download package. It highlights that the modification is non-commercial and developed by fans for fans, independent of Rockstar Games. GTA: United - GTAMods Wiki
Must be installed on a 100% clean, unmodified version of GTA San Andreas. The blog post at gtamodmafia
Existing San Andreas or older GTA United save games are not compatible and will cause crashes; a fresh start is required. new usable garages
Includes fixed rooftops, new usable garages, shops, and hundreds of accessible interiors that weren't in the original standalone games. The blog post at gtamodmafia
Version 1.2 was a major milestone released in 2012 after over four years of development. It introduced significant stability improvements, overhauled scripts, and a "limit adjustment system" to handle the massive map data.