You can plug it into the truck but it wouldn't hurt to plug it into the computer to make sure everything on that end is working. If there are any custom tunes from the original owner you WILL have to do an update to clear them and put the canned tunes back on.
For custom tunes follow this link to the order form.
Power Hungry Performance - Ordering Info
In your case I'd for sure get a 93 performance tune. You can get a lower octane performance tune but I'd just skip and use the 87 tow when you dont fill with the higher grade fuel and bump the timing up about .75-1 degrees. There is no specific mileage tune because those were lethargic and did not guarantee better mileage. Instead, good pedal control with the performance tune will be your best bet.