Can my phone be fixed without a high cost...?

i have a lg rumor. Its is old almost 2 years in sep. but now its batter life is around 1 min without the charger. I got a new phone so this phone isn't in service. The buttons don't work super well but that really isn't my problem. i need to know what is wrong with it and should i just get a new battery. I love this phone... Please tell me if there is a possible way to get it fixed.