you can file the business on Schedule C to form 1040 and then would not need an EIN. You do need the appropriate state and local licenses — whatever they are.

you depreciate the truck, see form 4562.

the interest paid on the loan to buy it is deductible on your Schedule C. so are fuel, repairs, insurance, license fees, etc. [Tires should probably be added to the value of the truck becuase you're depreciating the cost of the first set of tires.]

{all the “ordinary and necessary” expenses of running the business are deductible, even if that means you had a loss.}

[there are limits on losses -- you do have to show a profit in two years of each five.]

if you have a profit, you’ll also need Schedule SE.

does this help?

You may need a tax ID# to get a business license from the town where you live. The Health Department will want to see your business license.
Yes, you can write off the purchase price of the truck. Since you’re making payments, you’ll have to depreciate it rather than writing off the purchase price in the first year. Yes, you can write off the interest.
You can only claim home office expense for that square footage of your residence that is used exclusively for running your business. The best way to keep this straight is to set up a desk or something that you use *only* for the ice cream business. Home Business expenses are very detailed and specific (and strict) but they’re not difficult to understand.