Yes you can replace the HDD with an SSD (2.5" up to and including 2 TB). You can install a 1TB M.2 SATA SSD. The best source for a keyboard is right here. As for the fan, you guessed it, the same place here. Also the same place for a genuine Dell battery is here.
I know that Dell offically supports (only one of the below the below configurations) 1. But I wanted to know, is it possible to have one 512GB M.2 SSD & in the place of the 2.5-inch Hard Drive, can I have another 2.5-inch SATA SSD ofcourse of 1TB? 2. Leaving that(the above question) aside, (Again, I know that the official rating is just upto 512GB M.2 SATA SSD) But has anyone tested running 1TB SATA SSD M.2? Considering my current work load, 512GB is super right, So I would like to have a little breathing room  3. My niece accidentally, lifted up one on the keys of my Keyboard, so I would like to replace the keyboard, any suggestions as of where I can find some quality replacements? 4. The battery I think is depleated, it cannot even hold the power of 45mins of normal usage (Surfing the web mainly), so any good recommendations for the replacement? also, the fan seems to have become a lot more noisier than what it originally used to be, so any suggestions/solution to solve that issue are also welcome ;-). TIA.
I have a couple of questions about the upgrading the Storage & hardware 
replacements of Dell Inspiron 7560