Eclipse is a complicated game. If you have never taught the game yourself, expect a teaching game to take 4-7 hours.
It took me about 20-30 minutes to learn the game. I am an experienced gamer, had browsed the rulebook, and the player teaching me had taught others before. For a first-time teacher and inexperienced players, I estimate teaching will take at least an hour. While each one of the actions is relatively straightforward, there are a lot of them, and the way they interact is not always obvious.
As a small example of the complexity of the rules, consider the ability to take weakened Reaction actions after passing. First, players must remember that this is possible. They won't understand until they understand why you would want to do take these inefficient actions, and at least one player likely won't grasp why one player would pass before or after the rest. (The way the influence discs serve a dual purpose in choosing actions and controlling systems, while a beautiful mechanism, isn't like anything else your players are likely to have come across.)
Also consider, for example, the fact that every technology tile is referenced only by a name and icon. The icons provide a useful reminder of what the technology does, but in general the players will probably have to spend a lot of time referencing what potential technology purchases may do.
The fact that your players are relatively inexperienced at games in general may also mean the rules take longer to understand. For example, to an experienced gamer, the icon for a Reputation symbol outline and Ambassador outline clearly indicates "this is a spot that can hold either a Reputation tile or an Ambassador". To at least one of your inexperienced group, this will probably not be so intuitive and, like every other detail, it will have to be spelled out.
The BGG survey lists the best number of players as 4 or 6, and I agree; but I expect that a first game will take no less than an hour per player, plus teaching time. Expect it to take an entire evening or good chunk of a weekend day with a meal break. With experience the game can be made much quicker, but with entirely inexperienced players, it might even go longer.
Based on the tone of your question and your hesitance, I do not recommend that you purchase Eclipse with the expectation that this group will enjoy it. There is a good chance that they will not. If you can somehow borrow a copy, I would give it a try; I have also been told that the iPad version is quite good (and inexpensive). Playing on the iPad would not only let you know whether you like the game, but also give you familiarity with the rules which would make teaching much easier.