Is it possible to mod the DSL50 so that you can footswitch not only between the Classic and Ultra channels, but between OD1 and OD2 and between Clean and Crunch.

So basically like, swapping the buttons that are on the amp for footswitches?

how easy would this be, i've never modded an amp before i've done quite a bit of work on guitars though?
dyou know if there are any books i can get that give an introduction to this kind of thing, i dont really want to jump straight in?
For this particular mod? Not that I'm aware of.

There are several great electronics books, but there are less about amp building.

This mod isn't that complicated though. You'll need a 3-button footswitch (preferably with 2 1/4" TRS connections). One will continue to run what your old footswitch ran. The other will switch the channel modes.

You'll need to to run one lead from your heaters to the relay board (if you use the Weber board). Then run two leads leads from your 1/4" plug's tip and ring, and run one third lead from the shield of the plug that is grounded. Run wires from where the switches are to the board, and you are good.

Here's a great website about amp design, but it doesn't cover this topic:

Maybe, check around in the links to see if one of those sites cover channel switching.