FWIW, I decided against swapping my FMS during my upcoming timing belt job. I'm more concerned about the new seal leaking after I put it in than the old one leaking.
I am also doing my radiator hoses (since that system will be drained to replace the water pump), and my struts (which aren't really "related" but I suspect the timing belt replacement will be just a little easier if I do it with the passenger's side strut out of the car).
I agree with habbyguy and another vote against replacing FMS. If not leaking, don't touch it.
In addition to the radiator hose, I would also suggest replacing the thermostat.
Check the passenger side engine mount as well since that has to come off for timing belt change. If your MDX never had the front and side engine mount replaced, it's a good chance that it's shot.
Some also suggested to take the spark plugs out to be able to rotating the cranks easier but I ended up not taking the spark plugs out. However, if you plan to take them out, you may want to replace the spark plugs if it wasn't done recently.
My write up for your reference (sorry the picture is not pulling thanks to Photobucket ridiculous new policy).
FYI, I just ordered one more thing for my upcoming timing belt job... the right motor mount. I figure it's going to be out anyway, and it's only $30 or so delivered, and I KNOW the old one will fail two weeks after I go to the trouble of bolting it back in. ;-)
And FWIW, I also ordered the little plastic clips that hold the plastic splash panel in under the car, mainly because I go through at least a few a year working on other vehicles, even if I don't manage to break any of them doing the timing belt.
I suspect skirmich is right about new seals leaking, but I also haven't heard a lot about the MDX having main seals leaking. Now my '96 XJ Cherokee, OTOH... they're built to leak, particularly the rear, so if you've got the pan off it would be crazy to not replace the RMS (the only way to do it - fortunately it's a split seal so you don't have to drop the transmission).
I always replace the Main Seals and Never had an Instance when they leak.. I always go with OEM "NOK" Main Seals and never had a problem, When I did my AV6 Swap in my TL-S I replaced the RMS and haven´t had any leaks in 15K.
Well, I can happily report that having the right strut out of the car while changing the timing belt IS a good thing. There were a number of times when the extra access and visibility made things that much easier.
FWIW, it took eight hours (including cleaning up after) to do the following yesterday:
1) Change the timing belt
2) Change the front struts (including removing the springs from the old ones and reinstalling on the new ones, and replacing the mounts and upper bearings)
3) Change the radiator hoses (might as well since you have to drain the coolant anyway)
4) Change the right motor mount (surprising amount of extra effort because of the location of the third "hidden" bolt, but worth it, IMHO)
5) Change the accessory belt tensioner (it was getting noisy, and has to come off anyway, so no extra work for that)
6) Change the accessory belt (it looked great, but it makes no sense to NOT change it)
Now I just have to schedule a 4-wheel alignment (recently installed an adjustable rear upper control arms to bring my rear camber back into factory spec, and one tie rod end).
Busy day, but now I'm good to go for another 100,000 miles plus (which will take me well over 300,000 miles).