Attempt to swap the motherboard for changing firmware version
PS Vita Slim is really easy to tear apart comparing to other gadgets I had. Easy swap and it just works. Although I actually have an PS Vita Slim and the guide seems to be all about the PS Vita 1000 model, it went through easily.
The guide is an overkill. The L/R buttons does not require removal for replacing the motherboard.
Need to take extra care of the front camera though.
Use the iFixit Opening Tool to open from L/R buttons make opening the casing a charm.