I transplant trees all the time. Spruce are fairly easy to move beacause they do not have a tap root. Some pines like Scotch Pine have a deeper tap root, so you have to move them when they are only a couple years old.
These Norway Spruce were about 5-8 years old - and are about as big as you really want to move. The Root balls on these weighed about 50-100 lbs each. - But, they took real well -were planted in 2001 and are now 15-20 ft tall. I'd say it was worth the effort - I wished I'd planted them further apart - they touch now.
Seedlings I planted at the same time are now about 4-6 ft tall.
FH