I explained Decontamination in your Algae Post. It's basiclly Super Shocking your tub to kill off anything that could be growing in it. If your tub was sitting all summer with water in it, you definitely need to decontaminate. Even if you drained the tub, there still was water in the pipes, which would have built up some funky stuff. I would decontaminate either way. The question is, did you drain the water before letting it sit all summer?
A metal sequester will bind with the metals in the water, and prevent them from forming stains. However, it won't remove the metals. I don't know of any way to remove the metals, other than not put them in to begin with. That's why I recommend using a pre-filter. A great way to remove metal is to use a water softener. However a water softener will also remove Calcium (hence the reason why the water is softer), so you'll have to add it back. I don't know what type of metal sequester your local Spa store/dealer has in stock (there are many), but they can provide you with one.
What type of pH test kit did you get? I hope it's a drop test kit such as Taylor's. You really need a drop test kit to test pH and TA. Test Strips will not give very useful results, making it much harder to maintain your water.
Hi Yes it is a drop test kit, the tub was drained last summer, but of coarse there is always a little water left in it, so I will definately super shock it before I do anything else. Where do I pick up the filter for a hose? I have never seen one before? We are getting a water softner installed because our shower heads keep cloging.