PAX wardrobes are big and heavy and relatively time-consuming to assemble, particularly if you buy the new style with the sliding doors, but no IKEA furniture is difficult to assemble. You'll definitely need two people.
Besta and Billy furniture is easy to assemble. In general, the quality of all IKEA furniture above the basic level is fine. It won't last forever, but is solid and looks good. They tend to keep most of their designs up to date.