Answer to: How to fix square button?You can find a repair part to fix the PS Vita square,cross,round, triangle, start or select button here : http://www.consolereparatie.eu/contents/... Verry easy to fix it yourself, you can use the PS Vita teardown guide found on here : PlayStation Vita Teardown
Answer to: how-to on replacing Ps Vita screen?You can buy a full PS Vita screen assembly here: http://www.consolereparatie.eu/contents/... Or here : http://www.ebay.nl/itm/Sony-PS-Vita-oled-lcd-screen-touchscreen-front-assembly-replacement-repair-/161024079187?pt=LH_DefaultDomain_146&ha... Note - A full assembly is the only way to fix any problems with the OLED screen or touchscreen yourself. There is no way you can sepperate the OLED screen from the touchscreen faceplate without cracking or damaging both screens. I have tryed this a few times with already broken vita screens without any succes.
Answer to: Where to buy ps vita oled screenYou can find a complete front assambly here : http://www.consolereparatie.eu/contents/...