coax cable for tuner, any difference

Use the lowest loss cable possible. Quad shield RG-6 can be found at just about any "decent" supply house. Even Radio Shack has it or can get it.

In terms of whether or not this will help or hurt your signal depends. While you WILL incurr signal loss due to the longer run of cable, if you can get the antenna up quite a bit higher and out in the open, you'll more than make up for the loss. Sean
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I agree with Sean, and would just emphasize two points: Get the best shielded cable you can, and the installation will go much more smoothly if you can go with a cable that displays a "limp" pliability, instead of resisting you at every turn. The combination of these two factors will usually mean you'll have to spend a little bit more to get a quality cable that employs a finely braided internal shield construction along with a flexible jacket material. Also, gold plated terminations are desirable if you're placing the antenna outside for corrosion resistance. I was able to find these features at a fairly reasonable price in a Monster Cable product (sorry I don't remember the exact model), but mine is only 20' - I don't know if they make a 100' version.

Yes on the RG6. Depending on the results, you may want to invest in a antenna preamp to boost the signal.