512mb nvidia geforce g210 going out in hp

yes, graphics cards are pretty simple to change, tell me your price range, and i'd be happy to help, due to hp's 300 watt psu in the unit, it the options may be a bit smaller

If a 210 is enough for you, they tend to go for less than $50 USD, usually $30.
If you want to get a little more power but still relatively cheap, then a GT 430 tends to go for $50 - 70 USD.

As for changing the card itself, it's just a matter of unscrewing, removing, replacing, rescrewing. Just make sure you don't shock anything.