Quite right Sam. I'm 5ft 10inches for the record.
Lexy...this is how you change a text that has already been posted:
Click on your post and look at the buttons located in the top right hand corner. One of these will read 'Modify'
Click on this and your post will be presented to you ready for modification. Once you've completed the changes, you can either preview it first to make sure it is how you want it to read or just 'Save' it. Once you have depressed the Save' button your message will be posted as before. It will read 'modified at' in the bottom left hand corner of the message. It's a brilliant tool.
Hope that helps.
Lots of love
Roz