Ok, I just did something very similar to what you want to do, so I'll share what I found.
Your motherboard (I'm pretty sure) only supports SATA 3.0GB/s. Modern boards support SATA 6.0GB/s. What that means is that your SSD will be limited by the bandwidth that your SATA ports provide. You will not get the same read and write performance that the SSD manufacturer has listed on the specs. Despite this fact, I still recommend getting an SSD, and here is why:
Your access times on the SSD will still blow an HDD out of the water. You WILL notice a snappier response from an SSD and it will still read and write slightly faster than an HDD. Also, you mentioned that you want to upgrade your entire system eventually, and a good SSD today will still suit your needs a year or two from now.
Now to answer your questions:
1) EvilGenius is right. Any major brand with good reviews will be good. I personally like the Samsung 840 Pro and 840 Evo, but you will pay a bit more for them. Intel is my second favorite, and I would probably choose Corsair for third, but I don't have any experience with them.
2) Yes, but you would need to make sure that you get a large enough SSD if you want your games on there. 250GB is about the minimum these days. Instead of thinking about larger programs, think about which ones you want the most speed out of. For example, MS Office is a big set of programs, but who cares if it goes slow, right? So put stuff like that on the HDD.
3) It is just as easy to install an SSD in a computer as it is to install an HDD. Also, it is just as easy to install the operating system and programs. Once again, EvilGenius is right. You'll want to do a clean install to get the best performance.
The rest is advice that you didn't ask for, but I'm going to give anyway :D I would highly recommend getting an external hard drive and taking everything off your current HDD. Once you've done that shut down your computer, UNPLUG the HDD COMPLETELY and install the SSD. Once you've done that install your OS and the programs that you want to go fast on the SSD (remember, the SSD is the only drive you have plugged in). Once you get all of that configured, then shutdown your computer, plug the HDD back in, and format it. Now you have 500GB of space that is fresh and ready for your mass storage and slow programs.
The reason I say to install it that way is because I have heard several stories of older computers getting slightly confused during the installation process when there is an SSD and an HDD present. It is best to just remove the problem altogether.
Good luck and I hope this helps!