Welcome pewterpirate,
To give you an idea of good prices... (MarineDepot.com, Dr. Fosters and Smith, thatpetplace all have good prices)
powerhead(Maxijet 1200) $20 each.(two should be good enough for 75 gal)
-hydrometer(i have the Instant Ocean one) $8
-Lighting/hoods(there isn't on that comes with the tank?) If not and you aren't going the coral way then you should be able to find something cheap. Maybe $50-80. I would suggest the all glass tops just incase you plan to go into corals.
-Salt-(160 gal container) $30 you will go though your first bucket quickly
-heater - $20-30
-sand - I would recomend getting it from Lowes or Home Depot. 100lbs for $8. Otherwise you will spend a fortune. This may increase your cycle time to 3 months.
These last two are going to kick you in your nuts
-Skimmer- For a 75 gal. I wouldn't spend any less than $200. You want a quality skimmer for sure. This along with the Live Rock/sand is all you need to filter your tank.
-Live Rock - I would suggest 100 lbs for your tank size. You might need more, but this will get you started nicely. LR can be anywhere from $4 lb to $8 lb. If you want to cut some costs, get a 45 lb box online of LR from some where and toss that in with 55lbs of Base rock. Base rock you can get for around 1.50 a lb. but you gotta look hard to find it at that price.
Then you can wait about 3 months while all of this cycles....
Then you will need to add a clean up crew. (research this online, you have some time)
-Lots of people say you need a sump for a tank that size, but you should be ok without one. You can always add this later when you save up some more.
-Then fish!!
Hope this gives you a little picture. LR is not the creapest way to go, but you will love it when you get it. I'm going to post my pictures online soon of my LR to give you an idea. Keep an eye out for the post "buying live rock online"
-Nate