There are two limitations about which you asked (1) will if fit in the space allotted; and (2) will they sell me the amount I need?
The answer to the first one should be obvious when you get there, and only you can judge. The second is much more complex. On the one hand, I've never met a merchant unwilling to take as much of your money as you are willing to leave behind. At the same time, whether you can buy as much as you need depends slightly on how you are paying for it. Cash shouldn't be much of a problem as long as your wheelbarrow will hold it all. Credit cards, on the other hand, are another matter.
There are some times when you go to fill up and find that your credit card will only work for a set amount, usually $75, but could be anything, and unrelated to how much credit remains on your card. Do be aware that this amount is set by the CC company, and only for locations where there has been significant fraud in the past. The store has no control over this. It's one reason I have several credit cards so that if one chokes, surely another will work. I have had times when I had to use two cards in order to get the total amount needed. It's annoying, but I can't blame the CC company from wanting to limit their exposure.
Do be aware that there are enough rigs with large tanks running around that both issues are quite solvable.