zitozac,
This is also my first year doing the GS, but from what I gather, you should probably expect to pay about 0.5 cents for each mile. So if you hit 110,000, it may cost about $550. However, this is based on previous programs. The program this year is quite different.
Nobody will really be able to say how much it will cost until it has been completed. Good deals are likely to pop up as the contest is played.