If you are making up sliding jigs for the tablesaw or other tools, consider steel rather than wood for the guide runners. Steel runners won't swell like wood will during high humidity to cause sticking and binding. You can ask local steel suppliers for cold rolled steel to fit the grooves, or use runners from dismantled miter gauges. Steel takes a little more effort to mount, but will provide years of hassle-free service.
By sending in extra money each month or making an extra payment at the end of the year, you can accelerate the process of paying off the loan. When you send extra money, be sure to indicate that the excess payment is to be applied to the principal. Most lenders allow loan prepayment, though you may have to pay a prepayment penalty to do so. Ask your lender for details.