Good clean fun! I built mine myself just like you, with a few guys with a crane to put up trusses and roof panels, someone to pour/surface the concrete, and a guy to charge the heat pump with freon - everything else from the dirt work to the light switches. (I tell people I built it with my bare hands but I lie, I used tools.
Like you said, it took FAR longer than it would have if I'd had more than a crew of one (me). My motto is "You can't do everything the same day!" Hang in there: it is tremendously satisfying to work in a space you designed and built yourself. And the cost is SO much less! If you start getting burned out take a break - what I did was move a bandsaw and lathe in as soon as I had power so I could take a break and play when I got tired of insulating and putting up ceiling panels.
Hey, where do you live? Maybe someone close would come and help with siding or something.
BTW, mine is post and beam with 2x6 stud wall fill, 100 amps underground, industrial insulated garage doors, 24x62 overall. I do wish I had more space, but besides woodworking I have a small machine shop, welding shop, farm maintenance, electronics bench, office, and farm animal care areas inside too - if just for wood I'd be bouncing around in the extra space!) I am hoping to add an extension for a small kitchen and bathroom/shower after I save up some more money.
You are going to enjoy it so much! And it looks like it has a wonderful outside space and close to the house too. Oops, might be harder to hide! - I built my shop near my barn so if I don't answer the phone my Lovely Bride has to walk down the hill to find me.
Oh, one suggestion, something I did at my shop which has made life easier: I installed keypad deadbolts on the entry doors so I never have to carry a key with me. And I'd probably put a walk-through door in the partition wall.
Be sure to post more photos, outside and in, and a floor plan with tool placement too. Lots of people are interested in that.
JKJ