Will the GA-H81M-S2H work with a Samsung 850 EVO 250gb SSD and a Hitachi HDS721010DLE630 1TB HDD?

[Lunaerus]

I'm getting my very first SSD, and I have a few questions that I can hopefully run past you guys. 

1) My motherboard has 

2 x SATA 6Gb/s connectors (SATA3 0/1) and 2 x SATA 3Gb/s connectors (SATA2 2/3)

Will I be able to plug my future samsung EVO 250gb into one of the Sata 3 slots, and my Hitachi HDS721010DLE630 1tb HDD into the other? Is there enough slots for the both of them? 

2) I believe that there are 3 different types of 850 EVOs, 2.5", mSATA, and m.2. I assume the 2.5" is the best/only option for me considering my motherboard, is that true?

3) Once I get my SSD, I heard that all I have to do is unplug my HDD, plug in my SSD, and start up my PC, and it will begin downloading my windows 10 OS on my SSD. Is this the case? I don't have any disks with operating systems on them, and I bought my computer prebuilt with windows 8.1 (came with the windows product key on the side) then upgraded to windows 10 for free.

4) Do you guys think that there are any better options for SSD's considering my motherboard? I did some research and came to the conclusion that the Samsung 850 EVO 250GB would be the best option for the price. (Around $85)

5) My final question, my PC has been giving me the error: Windows detected a hard disk problem and has been asking me to back up all of my files to prevent information lost every since I got it almost a year ago. It says that my Hitachi HDD is the failing drive. I scanned my disk multiple times and have never found anything wrong with it... I've just been ignoring the message, which probably isn't a very good idea.

I hope my questions weren't too noobish for you guys, i'm some what new to the world of PC components.

[GDRRiley]

1 yes you could get 2 850evo drives and be fine. HDD can plug into any sata port and you wouldn't be able to tell the difference. 2) there are 2 types and yes the 2.5in is what you need. 4) it is one of the best SSD. 

[Lunaerus]

I just ran a program called Hard Disk Sentinel that was recommended to me, and got quite alarming results..

Performance: 100%
Health: 0%
Failure Predicted - Attribute: 5 Reallocated Sectors Count, Count of sectors moved to the spare area. Indicate problem with the disk surface or the read/write heads.
There are 1988 bad sectors on the disk surface. The contents of these sectors were moved to the spare area.
Based on the number of remapping operations, the health of the disk was decreased in different steps.
Replace hard disk immediately.

Not sure what to do now, if I replaced my HDD I won't be able to get the SSD