1) Macbook Pros are generally solid products, if there are reliability issues they usually manifest themselves within the first year or shortly after that, which is why AppleCare is generally recommended.
Since the components are indeed soldered on to the board, if the RAM dies for example, you would have to go to Apple to have it fixed, and if you're out of warranty...well you'll be paying through the nose for replacement parts, if you get AppleCare, by the time your machine does come out of warranty and does encounter hardware failure chances are that by the time this happens the newer machines run circles around the one you have, and its much cheaper to just get a new one.
This doesn't mean throw it away after two or three years (that's stupid), it means that if you get 5, 6, 7 years out of the system (which isn't unheard of, it more common than people think) then it doesn't make sense to try and save it when it does croak. Its gonna be a dinosaur next to the newer Macs or whatever comes out in 6 years, you'd be better served by just getting a new one at that point.
The most common recommendation you'll hear from people to extend the life of the notebook's performance is to spec it out as much as you can since you can't upgrade anything besides the SSD after purchase, so if you can afford the 16GB RAM upgrade, even if its overkill, it may be a good idea to do so, the same with storage. It really depends on what you are doing with it and what you expect to be doing in the near future with it, and your budget.
I personally went with 256GB SSD and 8GB, I don't need huge local storage on this thing as I've got a big tower with terabytes of storage for that purpose. The same idea for the RAM, I'm not going to be running multiple VMs, and I'm certainly not gonna run Final Cut Pro, Photoshop and Dreamweaver at the same time. Plus OS X Mavericks stretches the 8GB pretty far before yielding to the swapfile thanks to Memory Compression. As always YMMV.
I also think people are being a little too paranoid when it comes to the soldered components, as if because the components aren't user serviceable anymore they magically become more fragile and can break at any moment. Before this MacBook Pro I had a crappy Acer laptop for 7 years that was user serviceable, I never upgraded a single component and it ran without any issues whatsoever. (Aside from having really really crappy performance, but that's to be expected from a bargain basement Walmart computer.)
2) AppleCare extends the warranty an additional two years after the purchase date, so you get 3 years of coverage. You have one year from the purchase date to add on AppleCare. You cannot extend the warranty, so after 3 years your Mac enters the wilderness. If you take good care of your computer, it will last you as long as any other well cared for machine.
3) The MacBook Pro most certainly can handle all day usage, they might be (slightly) more expensive than a similarly specced PC, but they aren't dainty machines. Despite what others will tell you, Intel's Iris Graphics are no slouch, it performs quite well. The days of crappy Intel Integrated graphics are long gone.
You can attach it to your monitor via Thunderbolt to DVI adapters or HDMI.
Finally if you do encounter issues while under the warranty that you can't seem to fix, don't be afraid to just go to the Apple Store and have the Geniuses take a look at it, take advantage of AppleCare while you still can. Of course back up your Mac beforehand, just in case.
