The Feingold materials are mainly a "shopping guide" that lists brands that are feingold-approved- sometimes Brand A's peanut butter is acceptable while Brand B's is not. The organization sends out questionairres to food companies for them to fill out. Not all ingredients used in processing make it onto the package label, and trace amounts of TBHQ, BHA, or BHT can still affect some kids. Things like nuts can have preservatives in the packaging that aren't listed. Vitamin A palmitate is often preserved with BHA (but not always) and it will simply be listed as vitamin A palmitate on the label. It also includes brands of soaps, shampoos, household cleaners, etc, as synthetic fragrances from cleaning products are also problematic.
If you don't use any processed foods whatsoever, you don't need the food list. Any whole milk (lowfat and skim usually have vitamin A palmitate), butter, flour, sugar, raw beans or grains, raw meats and fish and fresh vegetables are acceptable. Any processed foods (breads, canned beans, yogurt, etc) may contain hidden chemical additives.
You should be able to find the list of salicilate-containing fruits and veggies (to be avoided in Stage 1) on the Feingold website. I'm no longer familiar with that list as we've been on Stage 2 for years.
Paying for the "new member packet" does make the program a LOT easier to implement. You can use some processed foods so your kids don't feel so left out when you're cutting out so many other foods from the diet. I used a lot of "approved junk food" (such as potato chips) when we were new on Feingold. It also gives you access to the members-only message board, which is a HUGE source of support and IMO a lot better than asking FG questions on MDC, as everybody there is familiar with the program.
Most "certified organic" processed foods are Feingold-acceptable (although many are Stage 2.) If you stay away from processed foods, and cook EVERYTHING from scratch, you can implement the program without paying for program materials. Or, you could implement "Feingold Lite", and just read labels, avoiding anything that lists artificial flavors or colors or TBHQ, BHT, or BHA, and taking a chance on hidden additives.