Word of advice, don't waste the money. It sounds like you know nothing about wide format printers and their maintenance. Purchasing them without any knowledge of software, fixing, repairing and cost of parts is the dumbest thing you could do.
Spend the money and buy a new valuejet 1638 and make sure to purchase additional training.
There are so many variables and issues that could plague a printer....and my first question would be why does the seller want to sell?