If you have something that gives back as much as these 20 year old trucks do, I say stick with it. Pertaining to transportation, is 5k truly even remotely a lot of money to consider to invest in a vehicle that will run for another 5 years? That's $2.74 cents per day invested into a working 4x4 Toyota that has proved itself as reliable if not more reliable than any "modern" truck today. If from a personal point of view there are aspects that appeal to you about a 15k vehicle, create a critical parts list on your 3rd gen for much less than 5k and fix those components and then go buy your 15k vehicle and have two. Youll find youll still want to drive the 3rd gen after a while, because it will keep the miles low on the one you're invested in 15k and over the long run this is the best investment because then you have a 3rd gen that's reliable, and something newer that is "hop in and drive across the country" reliable. These 3rd gens are some of the last vehicles that you can work on everything DIY with no formal special vehicle training. That in and of itself for me is worth keeping mine around forever. everyones gonna be driving electric trucks in 15 years and ill be in my 3rd gen haha