Help Touchwiz on my Galaxy S 3 not working need to reinstall?

[sandyr19522]

My phone came with this installed on my Samsung Galaxy S3 as the default launcher. Before I could switch to another, it did its damage....can't open any attachments to my emails, can't preview messages, just basically send plain emails and talk on the phone. Am going crazy because no one seems to be able to point me in the right direction. Tried restarting it several times, took battery out, to no avail. Please help???

Sandy Richardson
Galaxy S3 - AT&T network running on Kit Kat 4.2.2