Just keep playing until you beat the game, its not too hard. There's no alternative, unless you have AR MAX. And take my advice, get AR MAX. I used a code from that to get $99,999,999 and it kicks ***, I've filled up my garage in career mode with all fully-moded cars and I've still got $98,645,250. So either beat the game or get AR MAX (good stuff).
Which is worse? Being hole-punched to death or being eaten alive by the cast of "Friends"?