For the arm guard and quiver, get them new and get exactly what you want. Good quality ones will never wear out.
I prefer tabs to finger guards, and tabs have the bonus of being a lot cheaper. Buying another finger guard will set you back $8 - $20, whereas a tab will be $.5 - $1.5 and they wear out at about the same rate (ymmv). Some people work up to not needing any finger protection at all.
There's not much to say about strings except when you're buying new ones the sizing can be confusing. Write down what length your string is and verify that the new one is also that length. Some strings will be labeled by bow length. For example, if your bow is 60" then you need a 56" string (or thereabout). Some 56" strings will say 60" and what they mean is that they are for 60" BOWS. It can be confusing.
Arrows are by far the most expensive part of shooting. I'm afraid I don't have experience buying arrows in the last 10 years so I can't help you with cost/location, but it's definitely worth it to get some good arrows. Some places will let you pick out the materials, and I don't just mean the fletching colors - they'll give you a bunch of shafts and let you choose the ones you want to use (hint: put one end up to your eye and sight down the length while turning it. Only choose the straightest ones). Be careful about getting second-hand arrows. Since you're shooting a higher poundage bow it's especially important that your arrows are spined correctly. I won't get too much into it, but arrows that are less "dynamic" will bend unpredictably around your bow and decrease your accuracy. Basically, if you go online and buy some arrows from ebay, the arrows could be spined for a 25# or 30# bow and while you may not notice as a beginner, you will in the long run.
One of the biggest considerations should be the type of target you use. If the targets are very hard or the shooting area is surrounded by concrete or metal, your arrows will break far more quickly. All those arrows you chose so carefully? Kaput. On a funnier note, you can tell you're getting good when you start breaking your own arrows.
You don't mention whether you're an experienced archer, so I feel obliged to mention that 40# is a lot of draw weight and the people I know don't usually use anything above 35#. Also remember that the listed draw weight of the bow is usually at 28" - if you have long arms you'll be drawing more.
Best of luck! I love archery and wish I got out to shoot more.