It's so nice to meet a fellow Clydesdale owner!! :) She is gorgeous! I was in your shoes too at one point, brand new to drafts and had no clue what to do so I'll give you all the tips I picked up along the way from taking care of my Clydesdale.
Do a google search for draft tack. You'll find a number of different dealers and tack shops that have online stores to purchase from. Try also www.drafttack.com
As far as a saddle goes in my opinion Wintec's are awesome with their interchangeable gullet system. Some Clydes can be much narrower than others (like my guy for instance, he didn't take an extra wide gullet b/c he's narrow) so you can buy one saddle and just find the correct fit for her.
As for her feathers - brush them out all the time! Keep them clean and dry, especially take special care of them in muddy weather and in the cold. Feathers can freeze up in the winter time, become brittle and the hair will literally break off. The mud will also stay under their feathers and irritate the skin causing a fungal infection called scratches. Take the time when grooming them to brush them thoroughly so they neat and silky. Baby oil is what the Clydesdale owners use on their show horses to keep the feathers nice and silky. Just comb the baby oil through them. Also, baby powder and the big one the show horses use is corn starch to keep them nice and white. Do the same as with the baby oil, sprinkle it on and comb it through.
If you can afford it I would put her on a good joint supplement such as Grand Flex or SmartFlex from SmartPak (if you are inexperienced with horse supplements SmartPak has a hotline you can call to speak to someone who can help you). Because she is a larger horse maintaining healthy joints and a healthy muscular and skeletal system is very important.
That's all I can think of for now!! If you have any other specific questions just ask away. :) She's a gorgeous mare too! They are one of the sweetest, gentlest breed I've come across. Good luck with her!