Just a little problem, nothing serious

I bought a new laptop on a eletronics store (I'll give my 'older' one to my mother), and I got the last one in the store (clearly, the seller told me that it's the one used as sample) for a sightly-cheapier price.
When I checked it on home, the battery seems me to have some problems (the plugged but not charging issue) and it was used on exposition for almost one year (checking Norton antivirus, it was fully disabled, and with more than 210 days without a antivirus check)
Happily, as I bought it 3 days ago, I can to ask to the technical assistance to replace the battery, but possibly I cannot to 'renew' the hardware
What should I do? Take the laptop back to the store to change it for other one, a new one, or just send the battery to the technical assistance to replace it (still a little unsure about the hardware)?