[Sillium]

I think you have to configure mapchooser to get the extend vote:

// Specifies how many more frags are allowed when map is extended.
// -
// Default: "10"
// Minimum: "5.000000"
sm_extendmap_fragstep "10"

// Specifies how many more rounds each extension makes
// -
// Default: "5"
// Minimum: "5.000000"
sm_extendmap_roundstep "5"

// Specifies how much many more minutes each extension makes
// -
// Default: "15"
// Minimum: "5.000000"
sm_extendmap_timestep "15"

// Number of extensions allowed each map.
// -
// Default: "0"
// Minimum: "0.000000"
sm_mapvote_extend "1"

And for the second Part take a look at this: http://forums.alliedmods.net/showthread.php?t=91263
You want to change the nextmap and not the current map :-)