Here are some instructions for installing some of these products.
Hipshot D-tuner
Installing this tuner may be a retrofit but as often as not will require one or more existing tuner screw holes to be plugged and rebored. Sometimes it is very close but not quite right. Resist the temptation to try to finesse it and think that it will be "close enough". It won't be. Plug and rebore.
BA II
The BA II is a direct replacement for Fender guitars. The holes will match the holes in the body. If your guitar is not a Fender the body may require new holes to be bored (or old holes plugged and re-bored) to install the bridge. If the bridge has the standard saddles they will have to be slotted to one half the diameter of the individual string. This has been discussed on this forum recently. The search function should reveal some intelligent discussion on this subject.
The best advice that can be given is to not change anything until after your test. Unfamiliar equipment or changes to existing equipment is the easiest and quickest way to tank a performance.