yo,

my front brakes are startin to squeak (i realize this doesnt usually mean much with cars) and they dont seem to grab as much as before. its an old bike, 91, and im not sure what the previous owner did so maybe its time to get new pads. what are some signs to look for, short of takin the caliper apart and lookin at the pad? and is this an easy job, that someone who is mildly mechanically inclined could tackle?

peace.

Most pads have grooves cut in them, you should be able to see if they do using a flashlight. If you can't, and it looks like the pad material is about as thick, or thinner than the backing metal, you should change them. Pads can squeak and be fine though. I'm not sure if bikes usually have wear indicators like cars, they usually make more of a high pitched vibrating sound than a squeek.

Changing them is pretty easy. Service manual will tell you how, or probably some web articles out there. The haynes or clymer manuals will be specific to your bike though.

Also if you're not sure what's been done and your brake's don't grab as much, you should definately change the brake fluid. It's easy to do. Assume the worst, that you have 16 year old brake fluid, unless you know it's been changed. Unless it looks amber in the resivoir, change it.

Yao,

The GS's brakes tend to squeak, especially the back brake.  If the pads are good, getting the rear wheel aligned will help with the squeaking.

Ming.

Yeah some noise is normal, but you can see the brake pad material without removing the caliper and once it's much thinner than the backing plate it's time to replace it.

I replaced my brake pads just before I sold my bike with HH rated pads and WOW  I wish I did that earlier! They make a huge difference. Just get the cheap ones for the rear but if you're looking to improve your braking, get some HH for the front.

Of course fresh fluid and a braided line help too.