If you have a custom built PC, you will have to get the drivers from the support sites of the manufacturers of the components. I suspect likely most will come from the motherboard manufacturer.
The reasons you should get your drivers first is that you do not want to erase your system until you have them all. Actually, in more cases than not, the Win7 install process itself will supply most if not even all drivers it needs. In addition, the update
process itself will frequently find missing drivers and supply them. At the conclusion of the install process and before windows updates begin, the only missing driver that could cause you a problem is the network one. If that is installed in the install
process, I would not install any others, even if missing until after the windows update process is complete.
I have some very strong views about Microsoft updating. Ever since early 2015, Microsoft updating has become a risky process. They are frequently defective. For Win7 in particular, I object strongly to Microsoft converting my computer into a data collection
centre, which is what the non-security updates after 2014 do. If you disagree, and most do, then simply leave Windows Update turned on to automatic.
This is the update policy that I and my 135 client computers follow and have for quite some time. They have run completely reliably and stable for years now.
You may not need a new hard drive. It may well still be working now. However, you are about to expend a lot of time and effort to do the re-build. Statistically speaking, your drive is going to fail soon. Do you really want to wait for that? The cost
is not high. I also advise you to not consider SSD as a drive. Long story. A 7200 rpm drive will serve you well and perform.