First.... Check the bar: take it off the saw and set it on its edge, it should sit straight up; then flip it and try the other side; then look down the grooves and make sure they're straight (bar's not bent) and the "fingers" of the groove are even and equal and there's nothing clogging up the groove. Then, examine the sprocket tip for ease of movement and non-grittiness of the bearings. If all this passes, clean the bar: grab a putty knife or something similar and clean out the groove and with a small awl or something clean out the oil holes. Bar rail unevenness can be fixed but if you don't know what you're doing, it'd be better to just get a new bar.
OK, now......
Call Baileys @ 1-800-322-4539 and order the following:
Replaceable rim drive system: RD 100961 and you want a 7tooth rim in either .325 or 3/8.
I would say .325 since the chain is thinner and a thinner chain will cut a thinner kerf - which takes less power and athus a smaller saw will cut faster. Unless your bar is 3/8 and it's in good shape and you want to keep it (but I'd really recc. to change it)...
Look over your drive bearing and get a new one if it's worn, part number in the above part's description.
Get a spare sprocket. Once the first sprocket starts to wear, you're going to want to change it. Nice to have a spare so you don't wait for one to come in the mail. I'd send you to the website (baileys-online.com) but I don't know what size sprocket your rim will take. The nice person answering the phone will know.
While you're on the phone, ask for a new washer and eclip and a couple extra bar nuts. You'll lose one of them one day and you're dead in the water without them. What I do i paint them all bright red so I can find it easy when i "lose" it.
Now, if you want a new bar, their ArborMax or Arbor Pro bars are pretty nice for the price. Pick the length the same size as you have now and get a couple loops of chain as well. If your wood is mostly clean (none of the following: shaggy, gritty bark; rocks; you cut a lot of downed wood, etc...) get 2 loops of round chisel and one of semi-chisel. If you cut mostly dirty wood, 2 semi and chisel (for the clean stuff).
Make sure:
- the pitch (3/8 or .325) is the same for the sprocket the bar and the chain.
- the gauge (.043, .050, .058, etc...) is the same for the chain and bar.
- the number of drive links matches the chain loops and the bar.
Asking the Bailey's person will get you all squared away.
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About the only hard part of replacing the parts is the swap of the drum. Clean your crankshaft and bearing; put a dab of grease (axle grease) on the bearing and when you put the drum back on, line the groove/notch with the oil pump spring. If you rotate the drum while applying light pressure, it will just snap into place. Put the sprocket, washer and eclip back on and before you put the bar back on, start the saw and run it a little (not wide open) to see if the oil pump is putting out oil. When it does, you can put the bar and chain on it and go make some chips.
(and welcome to AS man! Enjoy your stay!) 
