well i will try to answer some of your questions. chlorella is a fresh water algae and is known as a super food because it is densely packed with all kinds of vitamins, minerals and enzymes. the health benefits are myriad and wide. here is a great site to read about it.
there are hundreds of places to buy it from, i hear good things about a product called "sun chlorella A"
the best juicer is much debated. i have both a lallane juicer and an omega 8003. the omega was $225 and the lallane was $90 on ebay. i use the lallane all the time, and think it works just fine. the omega also doubles as a wheatgrass juicer and nut butter maker, which the lalanne won't do. the problem with the omega is that when juicing produce it produces a very wet pulp which means there is a lot of juice left in there, i think it is very wasteful in that regard. here is a good website on various juicer and what they do.