You can not repair them,as they are under pressure.
And as far as upper and lower goes,if you can afford it just replace both at the same time,you'll be money ahead in the long run.
I'm having convertible problems. First off, I broke one of the clear hydraulic hoses. I want to repair it because that might be the easiest and cheapest route. Does any one know how to do this? If I do have to replace the hose, then how do I know which one to purchase? This one website asks to specify if its the upper or lower hose. http://store.convertibleparts.com/5973gmhse.html . Is there a test I can perform to find out which one is upper and which one is lower?