change watch battery

wasnt sure where to post this and thought this was the only place really, i have a adidas watch and wanting to change the battery and add a couple of links to lengthen the strap abit, so i need a tool to open the back of the watch to change the watch battery but not sure what tool it is, any ideas ? also i need a tool of some sort to change the links, its a metal strap with pins going threw it so im presuming there will be a tool to push the pins out from one side, then add the extra bits and push the pins back in, but again not sure which tool i need, anybody shed any light on whats needed please ? thanks

loads here

but when I did my watch just used a torx4 bit on a screwdriver and my leatherman. On the inside of the chain strap you should have arrows stamped into the links that can be removed, simply push pins out in that direction, once a bit is showing, pull out fully with the pliers (they are usually not a solid cylinder but a split 'V')

+1 on daveleebond's post.

I've got both Link Removal & Case Opener tools.

Both are cheap and will sit in a drawer for years, but they'll pay for themselves after one use compared to taking your watch to a jeweller.