Hi Frank - I'll have a go at tinkering with my saxophones, although I haven't tackled replacing a pad yet, I'd probably leave that to someone who knew what they were doing. When it comes to simpler things, such as adjusting spring tensions, lubricating moving parts, adjusting regulation, or finding and fixing leaks I'm quite willing to get in there and try it.
However, there are some useful things to remember - when making adjustments to springs or screws, it's a good idea to remember where you started and by how much you have made an adjustment (e.g. remember which screw you turned 1/4 turn and in what direction so if it makes the horn worse you know where to go to restore the screw to its original position); bearing in mind some horns have a lot of adjustment screws it is possible that adjusting a screw at one point can have an effect somewhere unexpected unless you can fix in your mind the relationship between various rods, cups, linking mechanisms etc.
Also, leaks can be fixed by very gently bending the cup so it seals evenly all around the tonehole - a tip I got from Griff is to place a reed between the cup and the tonehole on the opposite side to where you have found a leak, and push down gently over the point where you have a leak. By doing this, you don't risk bending anything too far out of whack, and it's possible to make quite small adjustments this way.
It's all good fun really, but be gentle with your horn and only make small adjustments, working towards the ideal and you should be ok.