While trying to set up an FTP server at my home years ago, I realized that my ISP had me behind a firewall in which tons of people displayed the same external IP address(I think I remembered it being called a NAT). I eventually gave up.
While reading up on OwnCloud, I saw mention a few times of DynDNS and related services that would allow users with temp IPs to still connect to their computer outside of the local network.
Would a service like this also allow someone like me to do the same? Does DynDNS act as a tunnel of sorts or is it just an IP tracker for people that have their own?
If it wouldn't suit my needs, is there some type of service or software I could use to end up with an externally accessible name or IP?
You use DynDNS to keep your personal IP current on DNS servers. You will need to have a unique domain name that DynDNS will track. DynDNS offers free sub-domain names you can use. If you intend to secure your server access with a private certificate, you cannot use a sub-domain and would need to purchase your own domain name. In either case you will have to have a unique WAN IP address on your router assigned by your ISP. If you have a shared IP address, you won't be able to set up access on the WAN to your home server. Your ISP may offer a static IP address that would work for you. The downside is that you will have to pay for a static IP address.
In the future ipv6 could be a solution. I have seen a few tunneling solutions but all were a bit pricy (couple of dollars/euros a month) so that you could also get a VPN service or spin your own VPN on a virtual private server.
Looks like you could have used syncthing or git-annex as well.