Give me a call on my cell as I bet you have a Midland/Haldex Pure Air Plus like me.
I just did mine and the next time I am in your area, I can stop by and help/show you if you would like.
FWIW, the dryer should be mounted on the PS-Rear frame rail near the primary fuel filter. You will most likely need a large strap type oil filter wrench or a large cam-type to loosen the filter enough to spin it off by hand. That is the coalescing filter. The dessicant cartridge resides inside the dryer body and is removed after the filter.
Both need to be changed at the same time.
Let me know what your paperwork shows (in your Spartan manual near the rear of the binder) and I'll see if it is the same model.
The kit with both items for mine is:
Midland Air Dryer:
Dessicant Filter: DA 33120
Coalescing Filter: DQ 6032
Air Dryer Filter Kit: DQ 6026 (includes both of the above items)
Here is the post where I did mine.
Does your dryer look like this one?
I got my parts from Colton Truck Supply in San Bernardino but there may be a place near you.