Here's my thoughts, which may not agree with anyone else's.
1. Oil and filter. I presume you're doing this at a time when an oil
change is needed.
2. Fuel filter. I believe the recommended interval is 52,500 miles. My
personal opinion is that 30k is a bit early for this and that the fuel
filter will likely last for much more than 60k.
3. PCV valve. I don't recall whether this is on the maintenance list in
the owner's manual. Very rarely have I ever seen one go bad, but it's
cheap enough to be worth doing anyway. If it plugs up and you get
excessive crankcase pressure, you could develop oil leaks.
4. Trans flush. Even though the recommended interval is 105k, I think
this service or a fluid drain and fill around 30k is a good idea. Well,
actually, I think the flush is a little excessive, but the drain and fill
is a good idea. For the most part, I don't recommend this service for the
customers where I work unless the fluid is really nasty or the vehicle is
actually in the neighborhood of 105k. To put this all in perspective, I'm
changing the fluid in my 1992 Taurus at 15k intervals. Tauruses are
notorious for transmission problems, and I'm attempting to see if I can
get the one I put in about 32k ago to last more than the seemingly normal
4. Coolant flush. You should do a flush or drain and fill every two
years, regardless of mileage. I do a drain and fill in my car every year,
but most people consider this overkill.
5. Piston cleaning. I'm not sure exactly what's being done here, but I
suspect it's some sort of induction (intake) system cleaning. Unless
there's some problem you're having that this will potentially solve, I'd
consider this pure fluff.
6. Multipoint and brake inspection. Most shops will do this for free
anyway. It's good to have done, but you really shouldn't consider this to
be substantially adding to the value of the service.
You should also consider replacing the timing belt. I know this is a
pricey item on this vehicle, but the maintenance interval is 4 years or
60k miles, whichever comes first. Presuming you're outside that period
since you have a 2001 XG, you should consider replacing it. Should the
belt break or strip, you'd be responsible for any damage that would cause
(except in California where it would appear that Hyundai cannot make you
change the timing belt to continue warranty coverage), and that would be
far more expensive than replacing the belt. Chances are, it'll last
another year, but if it doesn't, you'll probably see a repair bill the
size of which you've never seen before.
And I'll add that when the car is there, they may find things they want to
do to your car at additional expense. The service advisor should be able
to clearly explain to you why the service is recommended and the potential
consequences of not doing the service. If it sounds unclear or dubious,
tell them you'd like to think it over and then contact someone
knowledgeable who you know and trust. Too often, customers want to
understand about their cars and where their service money is going, but no
one gives them substantial information.