NezziR,
MasterBoard Warping:
I think there is a thread somewhere buried in here about warping Masterboards. The solution is really simple. Flip your board over and apply tiles to the opposite side as well. This will flatten out your board and offer you a completely new ground tile arrangement. The other thing to keep in mind is that this all depends on the type of glue youre using. Some white glues have a really high water content and tend to warp worse than others. My personal favorite at the moment is the UHU Office Pen by Saunders (VERY low water content).
Paper:
You can find 110lb cardstock at Staples and Walmart. Any office supply store should carry it in one form or another. If not in most cases they can order it in for you. I buy the Georgia-Pacific 110lb cardstock in a pack of 250 sheets. Lasts forever and the price is very reasonable.
Pens:
For "Edging" a black felt will suit most of your needs just fine. Any black felt will do. If you want the full spectrum and top of the line felts you can invest in a set of PrismaColors but they are expensive.
Hope that helps and happy folding
