i just recently quit my job, and they kept my final paycheck. what happened was i worked for a year, got some vacation time that i was informed of on my check stub next to my pay rate. i take said vacation i was informed i have earned. i quit 4 months later, they keep my final check because i took the vacation time too early.
can they legally do this? and do i have any means of getting my dang money?
You can threaten them, but the chances of you actually getting it are slim. First of all, can you prove (eg. timesheets) that you worked the last pay period? Do you have a copy of the company policy regarding vacation time? If you do you can try taking them to court over it, but again the burden of proof is on you. You can try calling your local Dept of Labor and see what they have to say but when something similar happened to me I got told it was my problem, they have no authority over businesses and their employees with regards to pay. YMMV, IANAL, etc…
My employment contract says something along the lines that I can take all my vacation from the beginning of the year, but if I leave I have to give back all but the pro-rated amount.
Where are you are located, would be a large factor in whether or not they can do this legally. In Calfiornia that vacation would be yours. Elsewhere the laws are different.
My company has two vacation pay policys California and everywhere else. If I don’t take all of my vacation I get a check, every other state the employee looses the time/money. 
Contact your local labor relations board (or whatever it is called in your neck of the woods) for an exact answer.
I would assume it would depend on how you get vacation time.
For example, at my company, we “accrue” a certain number of vacation hours per pay period. When we take vacation time, we can’t use up more than what we have banked (at least not without some management approval). Should I get fired or quit, those banked hours gets paid to me on my last paycheck. If I was negative, I would almost certainly owe them.
If you get alloted a certain number of hours in a lump amount to last for the whole year, you may owe the company for the days you took if you used up more than 1/3rd of them since you worked for 1/3rd of the year after getting them.
How much vacation had you earned, how much did you use, and how long was the work period the final check covered?
The best suggestion I can come up with is to speak with your ex-company’s HR department, have them show you the pertinent parts of the employment contract and/or employee handbook regarding vacation accrual and what happens to time used/not used if you get terminated.