2005 was the first year of the 2nd Gens so it was also the year with the most problems. CARFAX may be your best friend as to the history of the vehicle. If it has the original, failure-prone, radiator, it should have a Calsonic sticker on the top tank. If you see the P/N's: 21460-EA210, -EA265 or -EA200, it is original to the truck and you should plan on replacing it or bypassing it ASAP. If there is a 21460-9CA2E number, this means it was replaced with a Nissan radiator and "may" suggest that the cooler failed. Most of the radiators under the -9CA2E number were okay, but I've heard of a few cooler failures on the very early ones under this number. If there is no sticker on the top tank, it is likely an aftermarket replacement, which is fine, but "could" suggest a cooler failure occurred or it may just have been replaced as "preventative maintenance" or for a non-cooler related failure of the radiator. You'll want to pull the AT dipstick, which is held in with a 10MM head bolt, and look for signs of cross-contamination, which would be streaks of white in the fluid or, in worst cases, a pinkish custard.
Listen for a "whining" noise from the front of the engine that increases/decreases with the speed of the engine; it'll sound like a bad P/S pump to a degree. This is usually a sign that the upper timing chains have worn through the tensioner faces, which is an expensive repair.
This year/model would have had a "real" oil pressure gauge. If the needle pins too high, the oil pressure sensor is bad (not a huge deal); if the needle sits on the low side of the gauge while idling or running, it can be an indication that the gasket has failed on the back side of the rear timing cover, meaning the rear cover would need to be replaced---another expensive job. Normally, the oil gauge needle will sit right in the middle or just a little off-center.
If you have an OBD II code reader, check for codes. Common code-related problems are the fuel sending unit (faulty sender in tank), catalytic converter efficiency (bad converter), oxygen sensor (bad sensor) and cam position/crank position sensor codes (bad sensor---although one of these failing will also usually create a hard-starting or drivability concern).
Look for signs of gear oil (leaking axle seals) on the rear axle.
Operate all the modes of the HVAC system and listen for any "clicking" noises when the doors operate, which could indicate a bad mode door actuator (actuator isn't expensive, but requires dash removal to install).
Driveshaft U-joints and front wheel bearing hubs are also fairly common failures, but not necessarily deal breakers. It never hurts to have an independent shop or mechanic of your choosing inspect the vehicle, as well.
Thank you very much for the detailed info. This should be a huge help. I do plan on taking it to a shop to have it inspected but its always nice to know specific things to look out for. Thanks again.