A bit late ... but if this helps.
The elements and the solos (i.e. Part 1 and Part 2) aren't necessarily tested at the same time. You could, theoretically, do your Pre FS ELements all the way up to your Gold Elements, and never test a Part 2 (and still compete Preliminary!). You can also test Part 1 on one test day, and Part 2 on another; there's no problem with that at all, and you can test Part 2 before Part 1, or vice versa.
For elements, yes, the evaluators are rinkside. You will do your stroking first, then each of the elements in sequence (look at the test sheet for the order). If you're with a group, everyone will do each element before moving on to the next one. At the end, they will check to see if you've passed ALL of your stroking, and enough elements. If you haven't passed the stroking, and/or enough elements you'll get reskates if you're close enough to passing. For Prelim, you have to pass (i.e. get Satisfactory or higher) 12/14, and all of the stroking exercises. You can reskate up to 4 elements. In other words, if you get a "NI" on seven or more, you're not going to get reskates. Your coach is with you, and the evaluator will give you feedback on what needs to be improved. Note that you can retry an element several times - if the evaluator lets you.
For the program, you will skate the program; the judge will mark the sheet, the test chair gets it, and then you get it. It's just like your interpretive and your dance.
Attached is a link to the Prelim test sheet.
http://www.skatecanada-centralontario.com/Patrick%202010%202011/6%2029%2011%20Preliminary%20Freeskate%20test%20sheet%20July%201,2011.pdf