Making Your Own Mash Tun

I recently decided to build my own 10 gallon mash tun instead of ordering the preformulated one on the northern brewer website. I was able to find all the parts I needed at my local Home Depot or Lowes, with the exception of the 12 inch false bottom which I did order off of the website. In constructing it I did not realize till late that I should have gotten stainless steel parts. For the inside I got a nylon nipple to connect my hose to from the false bottom inside the cooler. The outside of the cooler has a plastic connector that goes to a brass valve and nipple. My concern here is will this set up create off flavors in my beers when I start to actually use it for all grain or am I just thinking too hard and worrying to much on all of this?

I would not worry about pvc in small amounts. I have seen many set ups using pvc valves they seem to work ok.