is it worthy to change the battery?

[preppystud]

mine seems to have battery problem. i am thinking about replacing the battery.

i don't know if the rest of the tablet will last any longer?

 

[smvim]

If you're reasonably handy with your gadgets offhand I'd say it's worth the effort:
https://www.ifixit.com/Guide/Nexus+7+Battery+Replacement/9895
... but a lot of that also depends on its current condition and how you much you use it. If you think you might get more out of upgrading to something newer, ask yourself if buying new is or isn't going to make that much of a difference in what you use your device to do now.

 

[GSDer]

mine seems to have battery problem

If by 'seems to have battery problem' you mean that it doesn't hold a charge like it used to, or degrades very quickly, and there's nothing else wrong with the device then I'd say it's a good investment.

You could also keep an eye on Woot - they occasionally have great deals on refurbished tablets and at the right price that might be better than getting a replacement battery.