I can't speak for any LBS, but many don't look too kindly on requests for installation of new hardware bought elsewhere. Don't take it personally if the staffer at the shop asks you "do you bring your own meat to Mcdonalds and ask them to make a burger?".
It's a sore point because most shops consider labor as an adjunct to support sales, and feel they can't survive on labor alone. Others are more open minded, but may charge more for labor alone than you'd want to pay.
Certainly you should be able to install pedals and a cassette, and ask the shop for labor on trimming the fork and installing it the headset and stem, which are related jobs anyway.
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