Setting up a VPN

My company needs to set up a VPN to a client of ours to run one of their applications off of. We are a call center, and will be setting up appointments for them, so we’ll also be accessing their client database. The client already has a VPN server in place, so will all we need to do is configure a client to access their server to run the application and access the database off of? Obviously we’ll have to open up some ports on our firewall to pass the VPN traffic, but I know how to take care of that anyways. They are wanting to bring a consultant in, because no one in the IT department has personally set one up before, but I think that would be a waste of money because I feel its do-able

TIA
Neal