Remove the battery before bringing it in. This offers the courtesy of lightening the bike so they can lift it onto a work stand, and it lets them know you don't expect them to work on the electric components or store the battery.
Rather than asking for a "full tune-up" it is much better to be specific about what you want. Asking them instead to check the derailleur & brakes (for example) tells them the bike has an attentive owner, limits the potential scope of the work, and reduces the shop's liability. After they've worked on your bike once, they will be more comfortable working on it in the future.
Some shops just do not work on e-bikes. This is a perfectly reasonable policy; say thanks and head on to the next shop. No need to call ahead: they will need to see the bike to know if it's something they can do.
