Differential service question?

I have been told by the dealer that the differential on my 03 2500Ram HD Diesel needs serviced ever 15K miles. This seems to be overkill. I have never changed the fluids after the first chnage when new on any other trucks I have owned. Is this something that really needs to be performed that often? The charge for this is $159. I think I could do it much cheaper than that.
One note, I do pull a 25ft fiver and Skeeter boat behind the fiver several times a year so it does get some pulling usage.

ok from what I have seen on a Schedule A which is normal use it is recommended to change the diff fluid every 45000 miles. BUT On a schedule B which is Severe Duty Use it is recommended every 15000 miles. I found this out on this maintanance schedule posted od dodgeram.org. the maintanance schedule is right here.
http://dodgeram.org/tech/dsl/maint/3rd_Gen-24v.htm\

One note about changing the differential fluids yourself is that if you have a 4x4 I don't think there is a drain plug in the front differential so you would need a pump in order to drain and fill it. They don't costs that much from what I ehar but I don't have one.

This is just an opinion but I wouldn`t pay the dealer that much. When I had to replace the pinion bearing on my rear end I didnt have a drain plug either all I did was put a drain pan underneath it and pulled the cover off when it was done draining all i did was clean the old gasket material off and used some rtv, put it back together and refill with the recommended weight oil, as far as just changing the oil in it you could do it in less than a half hour. I`ve never looked at the rear end of your particular year/model truck but a differential is a differential. I don`t know how mechanically inclined you are but you can always buy a haynes or chiltons manual. What crazy s said a pump would work I don`t know what they cost but i would find out and weigh it against the cost of some rtv every 15,000 miles

The Pump from what I see that some people have used is just a simple hand siphon pump. I found a link from a guy that has a Nissan Exterra and has done the siphoning with this pump that costs $10.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=37739
You can Also use the dodgetalk forum here and on this thread I found they have 2 pages of info on changing Transmission and Differentials and their opinions also. The vehicle they are discussing is a 3rd Generation RAM but the year is 04 where yours is 03 you said. But here is the link for your info.
http://www.dodgetalk.com/forums/showthread.php?t=41848&highlight=Changing+Fluid
Yes you could always just pop the two parts apart and drain it that way but then sometimes from what I have heard you could have leaks after putting the two parts back together. And depending how your front differential is setup pulling the front one apart can be a hassle. I did have a Chevy Blazer and in order for the dealer to pull my front differential apart they had to drop the axle and wheels. They did have a pump but for some reason their hand pump was too wide to fit in my hole I had. They ended up drilling a hole and plugging it instead. That was much cheaper but it is not recommended unless you would be draining a lot for offroad usage. I had my fluids drained at the time due to I ended up in 3 feet of water and had water on the interior and everythign was soaked. Got tired of that vehicle and bought a Dodge now.

ToBold didn`t mention if his truck was 4x4 but even if it is, if the front diff doesn`t get contaminated with water or something else or do alot of off road is there a need to change the oil in the front?

Well In my opinion If I change the one I will change the other also. BUT If you think about it the front is only engaged when you turn on your 4x4. So I foyu wanted to wait longer if you don't use your 4x4 much than I don't see a problem with changing them at different intervals. I am not a mechanic though but like I said I don't see a problem but I would still change both to be safe. If you use your 4x4 in winter only you might wanna change it before and after winter but if you hardly use your 4x4 it is kind of your call as to when you change it. BUT According to the maintance schedule posted on Dodgeram.org they should be changed at the same time.