if you want a several day loop on the east side that starts way up at elevation (and is easily done in 4 days):
drive up the cottonwood pass road. hike over cottonwood pass, head past chicken spring lake, go up miter basin, east climb up mt. pickering (13,500), up miter basin and over crabtree pass, down crabtree lakes to JMT, head south past mt. guyot, and back around, climb mount langley (14,000+), descend old army pass, back to car. (and watch your brakes on the drive back down)
but WATCH THE WEATHER FORECAST if you are up there in mid-October. it could do just about anything (though it will probably be nice).
also, one of the best things to do is just buy a few of the Tom Harrison maps for the Sierra, and a copy of Secor's book, and Choose Your Own Adventure.