1997 Buick Park avenue 3.8L 3800 series II Dynaride with 103,000 miles

One of my landscape customers was going to junk the car and I happen to intervene in time to acquire it. The story I received was that one day just a few miles from home the light came on and it started hesitating just enough to loose it's oomph and for the driver to notice things weren't quite right. She made it home, parked it and tried to start it multiple times without success before giving up and going out for a new ride. This was the first noticeable problem with the car but the couple is not car savvy in any way.

I had it towed home and am now in the process of repairing her, hopefully with your help, to the sweet ride she wants to be again (I hear her whispering to me).
Not having a clue more than guesses what the problem may be I started tinkering. I loaned out the OBDII scan tool from Advanced auto and got the code p0300 which translates to random/multiple cylinder misfire detected. I checked fuses, charged the battery, tried a bit of starter fluid in the TB, pulled every plug and they all sparked while cranking the engine. It's got fuel pressure at the rails. I checked the oil level and it was def. high so I pulled about 2 quarts out to get her into the hatched area of the dip stick.

The problems (or possibles) I see so far are that the plugs were wet with fuel and had a moderately dirty feel and appearance. I removed the air cleaner and housing and all were really clean. I tried to start it a couple times after pouring a bit of fuel into the plug holes and the car did a few very low muffled less than a cough sounds but I believe it did that before too. I then noticed a tan colored fluid coming from the TB and figured it not to be fuel as it smelled like antifreeze or brake fluid. I got curious and pulled the TB off the UIM and immediately saw things not right. The manifold side of the Tb is caked with soft (hardening as it dries tho) black deposit. The weird thing there was that when I manually opened the butterfly the other side of it was perfectly clean- night and day from one side of the butterfly to the other. I put the TB off to the side and looked into the manifold and saw pools of fluid in there, the roof of it soaked and everything dirty like the TB. Soooo I decided to at least pull the intake off for a cleaning and inspection. So I pulled the fuel rails, injectors, wires and whatever else was in the way of the intake coming out and then pulled it too. When it came off I could see that pool of fluid clearly and really began to think the problem is here or further in. The fluid was brown colored, slightly milky and the consistency of water. I shop vac'd it out and it seemed that there shouldn't be fluid there at all (no obvious coolant passages, to me). The EGR tube insides are also black, wet and fuel smelling. I also emptied most of the radiator fluid (about a half gallon, very low) and found it to be perfectly normal orange coolant without contaminants. I read a lot about this motor being notorious for it's intake manifold gasket failing due to that it has a plastic perimeter and that the manifold itself is plastic. My biggest question is how do I know for certainty where and how far to go. Is the Head gasket in question, rings, rods or anything else damaged that needs to be replaced? I'm ok with doing extensive work myself as long as I know what it is that I'm after, in other words diagnosing the problem IS my problem. I have no qualms with throwing a couple hundred bucks for parts and the time into it but the budget doesn't allow for much more, like professional service is not an option. I have pictures if anyone would like to see them of the car, the disassembled pieces and the pool of fluid also I can take any others that are asked of me. So in recap the car hasn't started or attempted to yet in my posession. I got it apart as far as the intake manifold. It cranks totally fine with no odd noises at all. I'm blaming the high oil level on a failed gasket somewhere and coolant mixing and bringing the level up but I'm posting cause I can't be sure. Should I just rip it down to change the head gaskets, valve cover gaskets and whatever else while it's being played with, is thhat the only way of knowing other th ings will be fine now? This will be the nicest car I've ever owned and I will really love to be cruising it this summer on some road trips and start pampering her with extras at the point I know she will survive for years to come. Any help, ideas or questions people will be of incalcuable value to me, many thanks in advance!! What do you think?
Eric