It looks like I'm losing oil from my rear end case, is it much of a deal to replace the seal? 33' brealaway
Is this something a shade tree mechanic can do or is it recomendid I check it into a shop?

Easy. Get a replacement gasket, and oil for the rear.

Take off the old, scrape and scrub the mating surfaces clean, put a lite film of gasket permatex on each surface and let it skin. Replace the bolts and torque to specs.

Should take about an hour tops.

It depends - and it's messy in any case.

What it depends on, is whether your gear case has has a bolted on plate in the rear, or if that plate is permanently mounted and the entire center section bolts on from the front.

If the former, no sweat except the mess. If the latter, the hassle factor rises greatly, as the axle shafts have to be pulled out part way to remove the center section and access the mating surfaces. That usually disturbs the outer seals which, to play it safe, should be replaced as well.

In any case, gear oil stinks, it's messier than motor oil, the smell clings, and it's a hassle to dispose of the drained oil.

When I was young and foolish, I'd tackle it either way, though one might find themself stuck in the middle of the learning curve removing the center section of a big truck axle the first time.

If the plate can be removed from the rear, and that's indeed where it's leaking, I'd tackle it even at my age. Today, if the center section has to be removed, I'd leave it to the pros, and swallow the expense.