I really don't know the specifics of your machine to speak as an expert on it, and I wouldn't even consider myself an expert on my machine, so take what I'm saying with that in mind!!!
I'm guessing maybe your guy doesn't recommend the upgrade to Yosemite because you only have 2GB of RAM? I think Yosemite does use more than Lion. My 2008 Mac Pro has bluetooth, I'm not sure if it came this way or it was added by the previous owner.
The Mac Pro can hold up to 4 internal hard drives - and I'm pretty sure you can get 1T drives for roughly $120 right now. It's probably less in the USA because of the dollar exchange rate. Personally, I use Time Machine to back my whole system up once a week - it's super easy to set up.
Adding hard drives is also super easy on this tower, the bays are designed to slide in and out like cartridges. You just need to know how to use a screwdriver.
RAM is super easy too - and there's lots of videos like this:
Honestly, if I can do it ANYONE can. This Mac Pro is fantastically designed for easy hardware upgrades - and it's one of the reasons I love it.
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