My old passport will expire soon and I need to renew my old?
It depends. I believe a travel agency will not be able to help you renew your passport - you would need to apply to your government, presumably through your nearest consulate. In some countries, travel agencies can indeed help to renew a visa (sometimes this is the preferred route, due to convenience or to avoid corruption). You dont say where youre applying, so I couldnt venture as to how viable this option is for you. Talk to other expats and - whatever you do - beware of scammers. If you can use a travel agency, they might be able to advise you about the best order in which to renew your passport and visa, and other queries like that that you may have.