ps3 problem!

hey guys i have 2 ps3s one of it doesnt work . you can only play demos and games you download the disc doesnt work you put the disc in the ps3 but it doesnt show on the tv and it doesnt work . do you guys know whats wrong i called sony they said they going to take $300 which means i can buy a new ps3 but i wanna fix it by myself so if you know how to fix it tell me

o same happend 2 me go 2 wats new and hav the game u wanted 2 play in n w8 4 wats new to load up and u shud see 3 games you last played if u dont clik a demo u hav load it up and then ps button and game shud be there otherwise i can help u,hoped this helped