If you just mess about with the planner the first time...then start again with you empty room...I found it much easier the second time. I found it helpful to think of how you would use the kitchen...first obviously where do you want you sink, cooker and fridge but also, what items do you want to store and where would you like to store them. Once you get your basic building blocks in place then you can mess around with different handles, worktops, trims, cover panels, etc.
It may seem daunting at first but once you start thinking about what you actually want in the kitchen, it does get a lot easier.
Regarding appointments, you have to ring Ikea and book...when I went up they were only doing midweek appointments but if you have your design completely put together on the planner then they will probably look through it quickly with you at weekends.
If you take extra care to include all the extras: coverpanels, legs, plinth, trims (if necessary), worktop, sink, taps, etc - then you won't really need a full appointment. I had an appointment booked but I knew exactly what I wanted and had spent ages making sure I had included all the extras, so the guy just looked over it, said it was fine and printed out the list of stuff we need to collect in the warehouse, while Ikea staff put together one half of the order (door fronts, etc)
Before I went up to Belfast for the appointment, I went online to their website with the itemised list from the planner and checked the stock of each item in the Belfast store as I had read on a forum beforehand that some people have to make a few trips up to get all the parts they need. The only thing that was out of stock for me was a black plinth so instead of going back up for that, I am planning on getting a sheet of MDF, cutting it to size and spraying it black....the cover panels I got were made of MDF anyway so I don't think it will make much of a difference.
Best of luck with it....the kitchens are really easy to put together and you will save a fortune.