I have a Asus RT-AC68U router and currently I can't seem to find a guide on how to actually install DD-WRT / Tomato on it does anyone have a link to a guide or the knowledge on how to do this I look at this and feel oh god what if I brick my router.
DD-WRT can be a little touchy to install. Each router is a little different. The firmware that works for Router A will probably not work for Router B, but also might work for Router B. You really need to know for sure before you start.
DD-WRT is a research project for everyone who uses it.
DD-WRT also requires a flash file before the first real version of DD-WRT is loaded. Loading the main firmware first may brick the router. You only do this one time. Subsequent updates can be loaded like all firmware.
The 30-30-30 reset is said to wreak havoc on Asus routers. Don't do it. Use whatever they write is appropriate for modern Asus routers.
Make sure you have good firmware. Research the release to see it's not buggy. I tried loading 25015 on my Netgear R6300 V1 and the 5GHz radio stopped working. Kong, the author, said I must have done something wrong. I didn't. I went back to 24200 and it popped back to life. Two later trials with 25015 had the same results. In other words, have a backup plan in case things don't work out.
Why not buy a refurbished router at low cost for experimentation. Don't try DD-WRT with your main household router if it works well and you need it as badly as you need your microwave oven in the kitchen. DD-WRT can make a router more stable if the stock firmware is buggy. It's also a fun home project. It's risky to play with your main router unless you don't mind telling your significant other you broke the internet.
I have 2 routers with DD-WRT, the R6300 V1 and a Netgear WNDR3400 V1. The latter is retired. I just bought a refurbished Netgear AC1450 and rechristened it as a R6300 V2 using Netgear firmware. Instructions how to convert are on my web site. The R6300 V2 is now my main router but will later be re-purposed as a 1300Mb ac bridge. I don't intend to put DD-WRT on the R6300 V2 unless the stock firmware doesn't meet my needs for some future use.