I just completed a project just like yours last year during the hottest part of the summer. It was rough work but it took us 3 days to complete. I was worried that installing the liner would be the hardest part but don't fret over that, it's the easy part and extra hands help out a ton but it can be done with two people.
First tip I would advise is to get very accurate numbers when measuring for a new liner. There are a few helpful vids on YouTube that I watched to help you understand how that is done. I watched a ton of them and learned little tidbits on each one. One thing you don't want to mess up on is the sloped surfaces when measuring. This is a little confusing but they need the lateral distance of the slope, not the distance of the slope itself. You will see what I mean in the videos.
While you are waiting on your liner you can be cleaning pools sub-surface. It looks like yours maybe concrete or possibly hard sand type surface. (I can't remember what the second surface is actually called). Either way you will need to clear it of everything. Bleaching the moss is what I done to mine too. Once dead I could run my fingers with some elbow grease and get the most of it off. Pull all of the weeds out too. Roundup, as suggested earlier, is a great idea too to make sure everything is dead. Be maticulous about cleaning the floor because you can feel everything through the liner.
Once cleaned you will need to patch repair the floor if it has any significant divots in it. Prolly not likely in a cement floor but with the sandy type surface I had, it was necessary. If this is what you have, you can talk with someone at the company you call to order the liner and they can suggest patching material for you. I used this
Marshalltown 14 in. x 4 in. Blue Steel Pool Trowel-Resilient Handle-PT144R-HD - The Home Depot and it was easy to trowel on this mixture. I think mine was a mixture of masonary sand and cement but can't remember the ratio. Then mist with water to get it somewhat pasty so it would stick to the slopes surfaces. Also clean the main drain, skimmer, and return plates too. You don't want any old gasket material or sealer on there when installing new liner.
For installing the liner Youtube is great again. Doheny's has a great video and a guy named Bill Tate has a great one too. This is pretty easy too. Tips, would be to make sure your corners all get lined up and in place and if you have to get in the liner, do it in sock feet. You will need a shop vac or vacs to suck the liner down while filling the pool. (You'll see how to in the videos.) Make sure the liner is exactly where you want it before filling. If it's not turn off vacs manipulate the liner slightly working wrinkles from center of pool to the bottom of the walls. Then turn on vac(s) again.
Only cut the liner for main drain after you have almost a foot of water in the bottom of pool and and the ring is screwed in place. Don't cut anything else out (slimmer, steps, or returns) until the water is just below their level.
I hope this helps you out and also that it was the kinda tips you were looking for....
