I was overseas for work while the shop did the work so I really didn't feel any time without my car, absolutely 0% was DIY other than ordering the parts lol. I think anyone handy could install the methanol kit there are many videos online on how to do it. The only gotcha parts are installing the tank and supporting it in the trunk, then drilling a line for the lines from the tank to the pump, or power and lines for the pump depending on where you want to install the pump. The parts were ~$1.5 (meth kit from Burger + Weistec charge pipe + Snow Performance Tank). Then my shop probably got another $2k in random parts...I wanted full easy disconnects, specific colored reinforced fluid lines, hidden pump, a different pump from the kit, fittings, etc. Then labor was the big part of the cost probably another $6K? hard to break out they were doing other stuff too. Again I wanted a completely hidden system besides the tank that is 100% reversible and there is absolutely no reason to take the car apart down to the frame to hide everything like they did, that's just me being picky - DIY could be installed pretty quickly in a day or two depending on your OCD levels.
You'll need some way to log and tune for the methanol so probably send your ECU back and forth from tuner along with log pulls, or if it's JB4 the whole new tune can be done remotely. No issues after installation other then fine tuning settings on the JB4 and tune. It's pretty simple stuff when it's installed correctly, you just have to live with it for a period of time to decide what conditions you want the spray to come on (boost, throttle, etc) and then some ability to log and see what the car is doing. Worth it! I just don't trust pump gas in general and on these hi strung motors cooling and antiknock insurance is great to have.