Battery replacement tools

[Edro]

I'm looking for some jewelers tools to replace the batteries in my watches. I'm not too sure if I have the terminology correct so please bear with me. I have a couple of fashion watches with a screw down backing (i.e. small notches in the steel cap on the back of the watch). One is a Bulova Marine Star and the other is a Kenneth Cole fashion watch. I have been taking them both to mall jewelers to replace the batteries for a few years. For some reason the past couple of years the batteries don't last more that 8 months and every time I take them in it's $10/battery replacement. I've tried 2 other different jewelers with the same result. Needless to say I started thinking maybe I could buy the batteries and do it myself. I'm thinking the batteries couldn't cost much more that $4...and paying someone $6 to do something so simple every 8 months doesn't seem worth it.

Both watches are labeled water resistant to 100M but I would never expose them to water as these are fashion watches and I doubt that they are truly water proof. So retaining "water resistance" when I put them back together after watch replacement is not my concern. I have a Suunto Vector that I use exclusively anytime I'm thinking of getting wet with my watch.

So my questions are:

What type of tools do I need? (tool names?)
Where can I get them?
Can you recommend one tool over another if there's more than one way to do this.

Where can I get watch batteries?
Are the tiny cell batteries labeled? (i.e. when I open the watch up, will I be able to read the battery type off of the battery itself?)

Any help would be greatly appreciated as I think investing into one or two tools to do this myself seems worthwhile.

Thanks,
Ed

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Wal-mart sells both batteries and the tool to remove most watch backs. I think the tool was 4.99 and most watch batteries are about $3. I found the tool with the batteries. It is adjustable to fit most backs.