Manicure and pedicure would be 30-45 minutes each so you at look at an half and a half total time I'd say. Most of that time is cutting/filing/prepping the nails. The Shellac itself is on quickly and total cure time is about 7 minutes per hand/foot.
In terms of doing anything before a pedicure I wouldn't, they will soak you feet and do all that kind of stuff for you. If you have any particularly bad areas of hard skin that you want to work on before you go then by all means do if it makes you feel happier but I don't worry too much.
Hope you love the Shellac as much as I do, I'm currently wearing Gotcha which is a pretty pink but I think Tutti Fruitti is my favourite.