At 131K that engine is just barely getting broken in. Are you sure it's a lifter tick and not an exhaust leak? Even at that, the lifters in these cars are not known to be quiet. With that said, mine did apparently have a lifter tick that I thought was a cracked rear manifold but ran up to 414k before the lifter finally showed itself and gave up. Funny part was even with the lifter issue it ran smooth, just got a noticible knock to it.

As far as the misfire, what have you replaced to try and resolve it? Is your car a GT or GTP?

Head gaskets are rare on these engines but can happen. And they also have a timing chain, no belt. And I've yet to change a stock one on any of my 3800's. One is at 300K and the other lived in the 414K engine I just pulled and I wasn't always kind to it and had no issues. But if you plan on having it pulled down to a shortblock then I'd replace the set while in there.

Would definetly go with TEP on the trans. Besides, they're only ~4 hours from you. You could pull it and drop it off/pickup in person and save a ton on shipping and get a road trip to boot. I only have 2 people that I would trust to build me a trans and Dave is one.