Obviously these are two very different questions, but I figure this is better than making two separate threads.
I've read up every site and tutorial I can find, but most aren't terribly helpful it seems unless you basically already know what you're doing anyway, and nowhere gives you any idea what final results will be like. So, I turn to you.

Both of these are relating to a crappy little Epi LP Junior. Yes, I know the body is crap wood and whatever. Normally, I'd never touch one of these, but that's exactly why I'm using it for this - if I screw it all up, it's no loss. And this isn't anything I'd be using on stage anyway, so yeah.

#1 on-board overdrive

The first (and to my understanding, the most simple) thing I have planned is to replace the tone knob to be on-board overdrive instead, like those 'black ice' systems sold on stewmac.
- Does anyone have any experience with this sort of thing, specifically, the final effect? Just how much overdrive and crunch do these kinds of things provide?
- I'm assuming at 10, it's providing the most overdrive it can. But what about at 0? Is it *completely* clean then, or is it something that will always have a slight effect?
- Since it'd mean losing the tone control, when/if the guitar is set to be 'clean' (i.e. at 0 I assume), what does in fact happen to the tone? Would it be how the guitar normally is at 0, 5, 10, or... well basically, how is the clean tone effected by this, not having control over it anymore.
- I hear these kinds of systems will also cause the volume to dip. Only a few places mention this though, so I'd just like clarification; would I end up having to adjust the volume knob all the time as well, is the dip not that noticeable, or in fact, is there any dip in volume at all?

#1 changing the bridge

LP Juniors have crappy bridges. Is it possible/how hard is it to change the bridge to something more like a tune-o-matic and stopbar as found on most LP-style guitars? Is it the sort of thing that requires stripping the entire guitar down and practically remaking it entirely, or is it a much more simple replacement?

Or, I've seen bridges for Fender guitars that can be set to a couple of pre-set tunings, so you can automatically tune down, flick to an open tuning, etc etc. I've looked for an LP equivalent but can't find anything. Are there such things for LPs? And if so, how hard are they to install, considering this Junior normally has just the one combination tailpiece/bridge (rather than the two separate bridge + stopbar: though if there are any which work for the normal LP bridge + stopbar combination, I'd like to know about those too)?