Looks like you can flash your existing router with DD-WRT.
http://dd-wrt.com/wiki/index.php/Linksys_E3200
You can download the factory firmware ahead of time to give you the option to revert back. I've used DD-WRT for 10 years now on many different routers. Currently I have it on a MOFI-3500 (DD-WRT native) since my primary internet for my home is on a 4G-LTE "aircard" via VZW. The MOFI allows me to share it throughout my home. I have two other older DD-WRT compatible router/APs acting as repeater-bridges to put desktops on the wireless and extend my range. I believe my MOFI has Dynamic DNS configuration options to help with the process. I admit I've not used Dynamic DNS or OpenVPN but I do have some interest in trying it out as well. I have Dish's Hopper, which has Sling built in for streaming live or recorded content. Since VZW wants $500 for a static (reserved DHCP) IP, I may try out the Dynamic DNS option to give me that ability.
Overall DD-WRT is great compared to the stock firmware so even if you don't use the OpenVPN, you've lost nothing.