Fyi cabelas is currently selling a vortex viper hd 10x42. It's the older version but it's amazing glass at $299. I'd look at that over the diamondback. It's way better and not much more money.
I like both nikon and leupold alot. I'd probably start by ditching the lower end leupolds. That being said ifnyou are gonna sell some scopes let me know what your getting rid of.
I just bought one from home depot amd installed it. Really isn't that big of a deal. Same thing I did 17 years ago when I needed one. Got that one at lowes. Easy install, works great. Use green bag of salt for nikon remover. You can get a hardness test strip to tell you what setting to use...