My mother's house is full of non-kosher cookware; Bill and I attempted to kasher some of the cookware so that Ezra could use it, but we found that plastic and glass could never be kashered; those materials must be bought new. Used baking sheets need to be blowtorched! But we could boil some metal and wood items. As long as every part of an item had been boiled for 30 seconds, it was pure.
As you can imagine, kashering even part of a kitchen is a complete pain in the ass. There is no reason to do it unless you truly believe that it is God's will that your cookware is ritually pure. I in fact don't believe this, but Ezra does, and I feel it is important that all Jews should be able to comfortably stay and eat at each others' homes. My plan is to reserve a small amount of cookware for vegetarian cooking and to buy some kosher food at Trader Joe's when a glatt kosher Jew stays over. Also, raw fruits and vegetables are always kosher, and luckily I always have those around.
Note: My great-grandmother and great-grandfather (a rabbi) ran a glatt kosher restaurant in Michigan for years!