I say go for it.
The issues with the transmission was in 00-03 models. A lot less in the 03. The issue was suppose to be the planetary gears exploding. However, I think it's something different. When I tore mine apart to inspect, it looked like the needle bearings for the planetary gears is the culprit. I believe the cage ended up going bad. Because of this, needle bearings became loose and lodging themselves into the planetary gear. Hence, the reason people think the issue originates from the planetary gears. If you need pics of what I'm talking about, I can provide those.
Also, this issue usually happened around the 75K mile mark. In your case, I would suggest pulling the pan and check out the 4 magnets on the bottom of the pan or at least draining the tranny fluid and checking the drain plug for fine metal dust or chunks of metal.
When the tundra first came out, there wasn't a lot of aftermarket products. Now there is but, we had to wait several years.
Overall, the truck is great! In my case, I chose not to mess with any of the engine stuff and keep it stock. The only aftermarket part I have or had, is a JBA EVOL(aka K&N, has the k&n stamp on it. Until K&N sold this division to JBA) muffler. Had a TRD drop, in and modified the stock air box, then upgraded to a AEM brute force intaked, then went back to stock air box (not modified).
If you end up getting the truck, let me know and I have a bunch of resources you can use to help out in any way...