Barb
I'm a retired builder, spent 35+years building homes etc.. If you go the package garage be aware that because of the size you are more than likely going to have to have a building permit, not that you can't put it up without one but you run the risk of possibly getting fined or worse case having to tear it down---I've seen that happen once when a particularly nasty, by-the-book building inspector became aware of the structure. The poor guy tried his best but the building dept. backed up the inspector and ordered it torn down. Not knowing your area or fees a national average is aprox 10% of the total cost to build. Another thing to consider is are you planning on running power for lights, outlets, 220v, in the future? If so and you are not capable of installing or running the electrical and higher an electrician, he will in all likelyhood pull a permit to CHA. That may cause a red flag on the structure by the building dept after the fact and you could face fines or worse for not having a permit.

Those pre-packaged garages are a bargain though the plans/product are rather generic in regards to meeting some local area codes for instance the roof trusses may not have but a minimum "snow load" factor--consult with the people you buy it from. I'm not familar with Menards but if it's like Lowes or Home Depot they should have some knowledgeable help in their "contractor" dept.

Fwiw and good luck--Gary