520lxi - Transaxle fluid change problem

Hi all, newcomer to the forum...

I recently acquired my first WH (came with the house), and love it. I just performed my first round of basic maintenance on it, and everything went well except changing the transaxle fluid.

Drained the oil, no problem. Changed the filter, it put up a fight but I won (a large hose runs diagonally across the filter, so you can't grip it from any angle, hard to even get a filter wrench on it). Putting the oil back in, here I have a problem. The first pint or so went right in. The next pint went in slower as air bubbled out past it, but went in at a reasonable pace. The next few pints trickled in over half an hour or so (each).

Now, I have less than half of the 4.5qts in it, and can't get any more oil to go in. Half a pint has sat in the funnel overnight, and shows no signs of taking any more. I suspect I somehow need to bleed out the air trapped in the transaxle, but see no way to do this. :banghead3

Any advice for a newbie?

Also, I have no intention of selling it, but just as a ballpark figure, how much would it cost to replace this thing? A fairly old (10+ years?) 520lxi, with ~300 hours on it... Basically, if something major breaks on it (I in no way claim myself as a skilled mechanic, as you can probably tell from my question ), should I bother having it fixed, or just plan on replacing it?

Thanks!