Steve, glad for your purchase. I have an 84 with almost 1800 hrs. To get to the hydro filter, drop the belly pan(plastic) filter is in front of transaxle, standard filter wrench, Mine has a drain plug in bottom of housing. Have you checked with Keeping it Green on this site, they might have a muffler. I have had problems with mine, mostly the mounting bracket, vibrations to the header pipe to muffler, have always welded back in place and continue to use. I have a 430 service manual, and will be glad to send you copies of things you run into. You might want to take the fender pan off, bolts on side in front and at seat, take safety connection loose, Take high/low range knob off, lift pan off, see the turnbuckle on the right side, if there is play, or slop, fittings might be worn, or just tighten, this is also where the creep can be adjusted out, best way I have found is to put rear on jack stands, run tractor and adjust turnbuckle,(for safety sake, I will inject, don't run tractor and attempt to adjust turnbuckle, because of proximity to drive shaft). I am by no means an expert on the tractor, but some here can and will assist you.
Ron