What's an estimated HIM finish time for a beginner?

With the very, very limited info I'd wager...

Swim: 54 to 60 minutes

Bike: 3:20 to 3:30

Run: 2:30 to 2:45

Finish time around 7 hours would be my guess.

Baring an injury, your speed over the next 6 weeks isn't likely to change much so extrapolate your long ride pace and long run pace into approximate 56 mile and 13 mile efforts.  

Can you go faster?  Probably...

Can you go slower?  Possibly...race day can be dramatically different than what you've experienced in training.  Consider the following examples.  What nutrition will you use for your HIM?  Get nutrition wrong, including the meals a day or two before the race, and all bets are off.  Have you done your long runs in the heat of the day?  Expect to be running 11AM--1PM or later which can be brutally hot, especially if you've been running at 5AM.  

6:51.27

Sounds like a better goal than one based on time.  Good luck & enjoy!

I'll respectfully disagree with JohnnyKay and a lot of other BT'ers who contribute greatly to this site and downplay time-based goals.  

The reality is almost every one of us has a number rattling around in our head about what a "good" race time will be.  It's important to acknowledge this and understand how to deal with it.  Pretending it doesn't exist isn't the right answer.  

It's also important to understand that there are things within your control and outside your control that influence this entirely arbitrary but highly personal time goal.  You can't control the weather, nor can you control the course (unless of course you're willing to become a RD and convince others to run your ideal course).  You have limited control over some other aspects of the race (you can take your bike in for a mechanical checkup and tune-up, but that only reduces the chance of a mechanical failure, it doesn't eliminate it).  Then there are things you can control which include whether you hit the snooze button or get up, get dressed, and exercise or whether you eat 4 brownies in one sitting.  You also control whether to do the tempo run or hill repeat called for in your training plan or switch to a leisurely pace/route because it's more comfortable.  

How important is it to hit your personal time goal?  Some people in this sport spent fantastic amounts of money on gear, special nutrition, training camps, coaches, reading materials, etc.  Some spend fantastic amounts of time training.  Each is a personal decision reflective of this goal compared with all of our other goals in life.  If you're like most of us, at the end of the race, whether you hit this time goal or not, you'll still have your full-time job, you'll still have a bed to sleep in, and you'll still have loved ones who love and respect you as much as they did before the race started.  

AlbertL has gone through in his head and estimated a 6:50--7:00 finish time.  Assume for a few minutes that race day conditions are ideal for AlbertL.  If he finishes in 6:48, he'll be very pleased that he finished faster than he expected.  If he finishes in 6:56, he'll still be happy...he finished within the range he expected, but will probably spend more time replaying parts of the race wondering where he could have shaved a minute here and a minute there.  If he finishes in 7:02, he'll probably have a nagging feeling that he should have been faster somewhere and somehow and will spend some time reflecting on his "unfinished business."  

Here's maybe another perspective:  

AlbertL, you pass the 12-mile mark on the run and look at your watch which shows 6:49:00.  You hurt, but you only have 1.1 miles to run and finish the race. If you can pick it up to a 10:00 min/mile pace, you can finish < 7:00:00.  Do you pick it up or do you shuffle along to cross in 7:01:18?  

There's only one right answer, and it comes from you, AlbertL, not me nor from JohnnyKay, nor anyone else.