Meanwhile, I've been running the same Gentoo install for ~9 years now (having migrated through 5 different machines). Rolling upgrades are awesome.
(It would be >10 years, but I did have to reinstall early on to migrate from x86 to x86-64).
The MHz number on the box is the bandwidth, not the sample rate. The sample rate is measured in samples per second (GSps). A 100MHz scope is probably adequate for analog signals up to 100MHz. However, if you're debugging a digital signal, you want a scope that has 3x the bandwidth of your signal's base frequency or more, because square waves are composed of the base frequency and an infinite number of harmonics. If you only have bandwidth for the base frequency, your square wave will be distorted into a sine wave and you won't be able to accurately see ringing, glitching, and other artifacts.
I have a 1GSps, 100MHz scope. I wouldn't use it for serious digital signal debugging above 30MHz (which is 33x lower than the sample rate), due to the bandwidth constraint. It's adequate for seeing if stuff up to 100-150MHz is "there" though (and for reading the bits out if you just want to use it as a poor man's logic analyzer), just don't expect to diagnose signal integrity and timing issues at those speeds.
Low-speed 1.8V and high-speed 0.5V LVDS mode, 800MHz... a MIPI-DSI display?