I'm not an expert in this field by any stretch of the imagination, so feel free to take what I say with a grain of salt.
I think you've been offered sound advice here already. My viewpoint comes from 50 years of life, not the publishing world. In that light, here's what I've learned:
For most of us, it's very difficult to not act (or react) based on our emotions. Life has proven that this very, very often comes with regrets, or at the very least, second thoughts. I've learned this the hard way far too many times and finally learned my lesson. Rarely do any decisions need to be made quickly. In business, which I do know well, any time quick decisions are being forced on you to perform a transaction, the word "no" will serve you well. When other people are pressuring you, it's usually for their benefit. People who do this tend to be impatient themselves, or are being pressured from someone else to make the sale.
It's in human nature to hear something that sounds great and want to believe it. Many people will even know in their heart that something isn't right about it, but want so desperately for it to be true, that they do it anyway. Diet pills, MLMs, etc.,
As writers, we all want to be published and sell well. We hear about reasonable sounding (or not so reasonable at times) offers from others in the industry - an industry overflowing with scams - but will still ask, "What if this one's legitimate though?"
Many, many, many writers have made emotional decisions like this and have regretted it.
Is the offer you mentioned legitimate and worthwhile? I don't know. But, what I do know, is that you shouldn't make your decision, especially saying yes, too quickly. If it's a "one time offer" or "special discount" if you act now... walk away. Follow the advice of others and research them fully. Find and contact other writers who have used their services and see how it worked for them.
My inclination is to decline, but that's me. I only want to publish the traditional way of submitting to agents and then finding a publisher. If I had to spend my own money to market and/or publish my own book, there's no way I would even begin step one of the process without researching the hell out of it and knowing every road, every path, every scam, and every detail of ever risk involved. Don't rely on luck. Rely on wisdom, patience and hard work.
Also, when you find something you really and truly want to do and be the best at, find a mentor. They're invaluable! Find one in the area of self-publishing. You'll be surprised how much those who have had success really do want to help others.
Lastly, I'm jealous you're from Iceland! If I had my life to live over again - knowing then what I know now - I would have moved to Iceland at the first opportunity! I wish you every success, my friend!