well, I just brewed a beer with 10 year old extract that came in a bag (it was liquid malt extract)
Others have had bad experiences with old extract though.
I would say might as well use it, it doesn't cost you anything if it doesn't taste any good.
If nothing else, it would be a good practice batch to get your process down before you spend your money on ingredients. If it does come out tasting horrible though, the extract could be to blame so don't let that put you off home brewing.
I'd say why not try them. Worst case the beer sux but hey you can at least get your first fermentation out of the way and learn the process. The yeast is is most likely expired so toss it and go buy a packet of dry ale yeast.
I took a bit of a haitus from 2001 to 2009. Had 5 cans of old LME left. Cans were bulged. Made a batch from 2 of the least bulged, threw the rest away - the beer was nasty (I still drank it, and didn't die).
If the cans are not bulged (spoiled), go ahead and use them, but I've read they will darken with age. The spoiled cans I used made a light pale ale recipe into a porter dark beer.
Bulged cans can indicate Botulism infection...definitely not something you want in your beer.
I have a bunch of those 6lb plastic jugs of LME from back when I was subscribed to Midwest's brew-of-the-month club, but didn't have enough time to brew. They're going on 2-3yrs old now. I brewed a porter last month with one of the 2yr old jugs that I'd kept refrigerated and it tastes a bit cidery, but is drinkable. I'm gonna use the rest exclusively for starters though, as I pressure-can those and can be sure of sterility and will be pouring off the beer from the yeast cake.
The yeast and hops are usually the most expensive part of the brew. IMO, it isn't worth it to make crappy beer. Just use it for starters.