So, you want to sell those old comics you found.
There's the quick, easy way and there's the thorough, possibly more profitable way.
I will warn you that comics of that era don't have a ton of value. There are a few issues that do (first appearance of certain characters, etc), but most not so much. Complete runs of a book are somewhat desirable if you can find the right buyer. That's where ebay comes in.
So, the quick way is to walk them into a comic store. The owner may give you a little something for them. Probably not much. Even if you go this way, you should educate yourself first. Many retailers are completely honest and will pay what they think is fair. Many. Not all, I would guess. You can look the issues on ebay, searching for the same issues that have sold. If you log in to ebay, you are allowed to search completed auctions. That will tell you what the market looks like. For example, I just searched "rom spaceknight lot" (lot means you have many issues) and found some sold items. One set of issues 1-35 in NM condition, sold for $27.
If you want to walk into a comic store to sell, it would be a good idea to look the stuff up like that on ebay, just to get an idea what the worth is. Doesn't mean you'll get that much, but it might alert you if there's something valuable in his collection.
If you want to go the more thorough route, you can just sell the stuff on ebay yourselves. That's not super easy. You need to have photos or scans of the books, you need to be very honest and critical about the condition they're in (the buyers will be, trust me), and you have to deal with shipping. It's the best way to maximize your profits, but it's a pain, especially for the relatively small amount of money involved (I'm assuming).
That's all I got. Hope you can turn them into something. The back issue market is not especially strong for books from the last 30 years or so.