For what it's worth--we did "ferberize" Sammy at around 4 1/2 months, at the recommendation of his doctor. BUT (and this is a big but) the situation was pretty different. Sammy clearly could self-soothe, and had been able to get himself to sleep on his own a few times at around 3 months. He also had a few weeks of only 2 wakings during the night. Then my husband started rocking him to sleep, and Sammy started waking up every 1 1/2 hours all night. I let this go for almost a month, nursing him every time, so I was pretty sure that he wasn't teething or sick (he also kept his normal nursing schedule during the day.) So we did do the Ferber method, and I was glad we did. It took 3 nights--each time we checked him and talked to him every 5, then 10, then 15 minutes. First night an hour total, second night 1/2 hour, third night 10 minutes. Now at 7 months he falls asleep easily on his own (at around 8pm, after a consistent bedtime routine), only wakes once or twice to eat at night, and has two pretty consistent 1 to 2 hour naps (and sometimes a third) every day. (Note that using this method does not mean that you let them cry every time they wake up--I still feed him at night, because I think his night wakings now are clearly from hunger, or getting cold, or another problem and not due to habit as they were before.) I'm only telling this story because I think the method is getting a bit of a bad rap here, and I want other people to know that it did work great for us. I don't think this really applies to Sydney.
But Traci, I DO NOT think that you should do it. I agree with others-I've been following your posts and I think Sydney needs a fuller medical workup. It sounds like it may be reflux, or something else--I think this may be more than just fussiness. Also, she needs to be older, or at least show some capacity to self-soothe before Ferber will work. It will just end up stressing you both out.
My pediatrician did also recommend the Ferber method--but all of her other advice has been very up to date, and I didn't do it just because she said so, but because I read up on the various options and decided this was the best one for us to try.