OEM is original equipment manufacturer, term gets referred to quite a bit.
Sorry to say, and no offense intended, but the headgasket is the same, has not changed. It could be due to the aluminum head, but again, no official explainantion has been offered to me. If the explaination for somehting like this isn't on the pretty stationary with the star in the corner, or told to me by a guy with a white lab coat on, I don't take alot of stock in it. I believe what paul is referring to is the modular vee engines use a sealant on the headgasket.
As far as doing other work on the engine, it's more of a personal decision on going ahead and replacing rings and bearings and so forth. I recommend basing the decision on what your plans are for the car. If you'd like to drive it say another 100,000 miles, the engine should handle that OK, just do what is needed. If you'd like to drive the car "indefinitely", then maybe you could look at just putting in a MB (or other, such as Metric) reman engine in it. Usually, of course, the reman route is for blown engines, not a blown headgasket car, so this would be a little extreme, in my book, but thought I'd throw it out there anyways. I don't really favor the "middle of the road" approach of just trying to fo rings and main/conrod bearings and so forth in the field. To do a good job it really should be done by a specialist to get a good job done. By the time you get done screwing around with all that, your money ahead to get a reman engine, plus if you get an MB reman the warranty is pretty good, too, 3 years I think it is. Well, dwell on that for awhile, anyways. i recommend making sure the cooling system gets flushed out a number of times. One recommendation I heard is to use marine bilge cleaner and water to do the initial flush to help get oil out od the cooling system. You could consider getting the radiator cleaned seperately at a radiator shop also. If the work is done soon, you shouldn't need to worry about the hoses on the car, extended periods of operation will lead to hose failures. I also recommend a new pressure tank( the one coolant is added to), plus there is an expansion tank in the right fender that you can't see that should be replaced also, as it will hold oily gunk in it and eventually be intro'd to the cooling system later...