I really need advice on a very large resurfacing/remodeling/construction pool project

Alright guys, I seriously need some advice here (and greatly appreciate any/all you give, even if it's burn it down and get out). My wife and I bought our house a few years ago, we are young, dumb, and naive. We didn't get a pool inspection, our inspector told us the wall wasnt that big of a deal, and we've had nothing but bad luck when it comes to other elements within the house. So now we are looking at the project below:

Pool size: 35-40k gallons, 20' x 40' main + 10' x 40' laplane + 7 x 7 hottub
Project details:
- pool needs to be resurfaced
- remove ~30ft from the laplane;
- there are also some cracks that need to be addressed (i think?)
- a pool company told me that I need to remove the surrounding stone and reset the edges
- Replace the filter (it's a cartridge filter now, no where near big enough)
- add a salt system (I've only had it for a year I'm already tired of dealing with algae blooms)
- replace a 90' wide, 5'6" retaining wall that is falling apart

As my wife and I really don't have the 35-45k that we are getting quoted to do the project (not including filters, chlorination systems) we are trying to come up with clever ways to save money.

For the wall, we plan to build a new one about 2-3 feet from the existing structure. We will only bring in professionals on the initial lay and when we need to geogrid because it requires taking down half of the other wall).

I've found some awesome deals on filters and salt systems on ebay from reputable companies so I'm square there. I can install them myself.

Since I can't actually plaster myself and I'm not able to, or know how to, hire plaster people directly I came up with the idea of tiling the entire pool in glass. I found a way to actually get large quantities of it straight from the manufacturers in china, korea, etc. I'm seeing prices in the $2-$3 a square foot range for tile i'm finding online at $10-$15 square foot. As my roughly calculated square footage is 1800 then I'm looking at about $3k-$5k for tile which seems reasonable.

Unfortunately pool companies are asking $10 a square foot to lay the tile which seems absurd to me. Is there really that much work in laying tile that justifies $10 a square foot? Is there anything different about glass pool tile in a pool vs a backsplash in a kitchen? I'm asking because I'm trying to figure out if I can pay some guys $10-$12 an hour in cash (I'm the deep south, that's decent money down here) and not have to worry about my pool falling apart in a few months.

Also, the pool tile comes in several thicknesses. The cheapest of them is 4mm. It seems to be pretty common (at least in terms of what they are trying to sell) but they also have 8mm up to 25mm. Is there any harm in going with 4mm vs 8 or even 25? Does the higher thickness help with anything or is it purely aesthetic?

Thanks for taking the time to read my post. Again, I greatly appreciate any/all feedback. If you know of any other ways I could potentially knock some cash off of this project, I'm definitely listening. If you think that we shouldn't do anything I've listed, I'm also listening. Thanks!