Very well said bull.
Each person will have their own preferences. You can't know what you want until you brew a few times. As far as just converting the kegs, It is safe to say go ahead and add a SS Ball Valve either welded or not
Since your kegs are Aluminum and not the standard Stainless you will want to boil some water in them for a protective layer before boiling any wort in them. I don't know the science behind it but just search Aluminum on this forum and you'll find plenty. Look around the DIY forum and also check out this thread
for some ideas on what other people are doing. It'll give you an idea of how many options there are out there.