All really good advice given. For the "Eagles" style of distortion, I think I know what you mean.. its a fairly bright tone, and not too heavy on the amount of distortion or length of sustain... are you thinking of stuff like "Life in the Fast Lane"? If so, keep in mind that back in those days, they would get a lot of their "distortion" or "overdrive" for recording by simply turning up a quality tube amp as loud as it needs to be in order to get a nice, "clean" overdrive sound. I know "clean" doesn't make much sense, but what I mean is, its not this "wall of amps" howling lead sound. Its crisp and each note is relatively easy to hear.

I think its hard for many players now to appreciate just how different playing through a hard driven amp is compared to pedals or especially "amp simulators". The real thing is subtle, but distinctly different. Kind of like when you rent a movie, and you can tell it was shot on video, not film.

Good news though is that the pedals, amps and simulators available will do a really good job. For your pedal, I'd say keep the output quite high, but the amount of distortion fairly low. For amps, its finding that perfect blend of master gain/channel gain. If you keep the Master Gain really low, but roll the Channel Gain up high, the amp will over-drive, but probably too much... if so, roll back the Channel Gain and add more Master until you find the right mix. If you're working with an amp simulator, try looking for a Marshall JCM 50w preset, and play with that. You should be able to get pretty close.