I have a mid 2012 cMBP and have just ordered a new 512gb SSD and 16gb of ram. I am ok with the physical installation of the items as there are enough guides and I have a bit of experience. I just want to check that the OS installation will work properly. I have an external HD which I have installed Yosemite on and I can boot from that or my current HD. When I install my new SSD I presume I can boot from the external HD, format the newly installed SSD and then install a new, fresh version of Yosemite onto the SSD. I don't need to copy my current install and actually want to start from a fully fresh and clean install. Will this work? Thanks.