Dan, this is a great topic as many newbies experience questions like yours.
First its your money. Spend it with a shop you are comfortable with. Make sure their business practice matches your expectations. If not make sure they explain their business practice.
The shop appearance is a small part of things, but as many shop owners should take note – it is very important and sets the tone for the clients opinions.
Now as to your question of hand holding. Great question. Firstly a proper shop should either sell you an operational kart and then offer advice as post sale service. They can offer mechanical assistance for a fee and coaching as well.
If you buy a roller from them they should be extra patient in your ten visits to buy parts and recieve guidance in assembly (at a distance).
If you buy a roller or parts on your own or online they should offer you service at their shop rate for every minute.
In the end you should get a good kart together, the shop should pay the rent, buy some bread and order some iiTunes for their kids.