Indeed, resets are every wednesday regardless of when you start it.
If you donwload a couple mods (Atlas and Atlas Loot) you can see boss drops for every instance in game and make a list of whats worth going for and what isnt. Generally each boss in Kara drops a nice tanking peice but you have to get lucky. Ive ran it way over 20 times on my tankadin and Moroes has never dropped his tanking peice and maiden hasnt dropped either of the 2 she carrys
Getting a Kara guild shouldnt be a problem, there always guildes at that level and becuase its only 10 people it doesnt involve alot of effort to arrange. Keep your eyes open on the offical wow forums (Guild section).
Be warned tho you might get frustrated quickly
when we started off Kara it was taking us 3 nights to clear the place and alot of wipes, its a whole new level above normal 5mans. After a couple of months tho when everyone has tactics sorted and gear has slightly improved you will do a whole clear in a few hours (2hours 45min was last count methinks).