Charles Baetsen generously published the build notes for his backyard observatory dome, shown here.
Surprising to me, the wood (mainly sheets of 1/8-inch masonite and 1/2-plywood) was only about a third of the cost. Most of the money went into "little things" like paint, trim, caulking and hardware. You can do most of the work by yourself with a few good tools (primarily a jigsaw and router), but some aspects will require help from others (i.e., tracing out the gords and lifting the dome in place).
I would highly recommend pursuing such a project. The three weeks of hard work will reward you for decades of use.