I just was wondering if I am going to put it close to a wall, how you actually get to the plumbing to connect it up.
The short answer if it's against the wall is...with difficulty and with extra hands. If it has to be right up against the wall for weight distribution reasons, I would honestly rethink the size and/or location. Getting things behind a tank with only inches to spare and having to ask a family member to hold something and grab this tube or that thing as I'm trying to get it into the right place...I'm so done with that LOL. I make sure I can actually fit myself behind the tank these days, although it's been a long time since did a big tank. Still, if I ever do one again, I will be leaving ample space to access the back.
So how much do you think you would save my buying the tank, overflow, plumbing, stand (I Can make my own), sump, etc, rather than buying a complete new all-in-one system? 10%, 25% 50%?
Hard for me to give you an exact number there. I haven't been in the market for new equipment lately, but many years back I contemplated I think what was a 30gal cube kit because it was slick-looking but ended up doing a 55gal with similar equipment for probably about the same price. That's about the best comparison I can give you from my own experience. That was also a different market though. These days the price of lumber is pretty absurd right not when considering tank stands, so that's one individual item where prefab might actually be cheaper even if everything else is DIY.
Also I have never drilled a tank before. All the videos say it is easy, but man if you buy a big ticket tank and screw up the drilling ... ouch.
The rule of thumb I always heard though was acrylic is "easy," regular glass less so, and don't even try it on tempered glass because the whole pane can just explode on you. While I have not drilled a tank specifically, I have recently drilled acrylic panels for other reasons; I use them for windows and other things on chicken coops. I think different people probably define "easy" rather differently with the drilling task. For my acrylic coop panels, I had a 75% success rate on the last panel I drilled that needed 4 small holes. 3 holes were perfect and the last one...the drill went through kind of weird right as it exited the other side. I don't know if it wobbled or hit some irregularity in the acrylic, but the result was an instant 2" crack in the panel radiating out from the hole. If the tank is a big expense and you don't want to risk it, buy a pre-drilled tank or use an overflow box (of course overflow boxes have their own issues...).
For example Waterbox has a 148 gallon that is listed as 418 lbs by itself.
Huh...must be thicker/heavier glass due to the bigger volume it holds. Biggest I've done is 55gal glass tank which I could lift myself (admittedly quite awkwardly at my short height, I prefer to have help) so maybe I just don't have a good intuition for how the weight scales as the tank grows, but I've seen two guys move a 100gal, and I've seen two guys move a 6ft grand piano that was about 500lbs. This is not something I've done myself, but if you need to move something big, quite heavy, and very fragile and don't get any other suggestions...you might actually see if a small piano moving company would be willing shift something that isn't an instrument just to get the things from the pallet into the house. Piano movers in my experience are typically a bit bigger dudes and also more careful than the average set of guys that deal with moving furniture and such.
Can you actually get those things in the house, put the stand in place close to the wall, put the tank on top and plumb it while it is in position, or do you have to assemble it, then move it into place?
I'd think you'd absolutely have to bring it in a piece at a time, otherwise you risk destroying the more fragile bits. Do make sure you check your door width and any turns it has to make relative to the size of the pieces coming in. When I brought my 55gal home I didn't do that and had to turn it on its end to get it round one of the doors, which is probably not something that can reasonably be done with a much larger tank.