Sounds like a good buy.

Definitely pull out the flame trap and clean it. No need to replace it. Just take a drill bit and clean out the passages. Also make sure the vacuum hose is intact, and clean the port where the vacuum hose from the flame trap attaches to the intake manifold. Try to blow into the big hose that goes from the flame trap down to the oil separator box on the driver side of the engine. At 135k mi, it should still flow just fine, but it is best to make sure it is clear. Removing the flame trap is a real pain. Don't be surprised if you break the plastic trap holder. They get brittle with age but they are cheap to replace.

Take a good look at the lead to your crank position sensor. The lead runs down the back of the engine and the sensor bolts in to the top center of the bell housing. That sensor should have been replaced by now, but if the lead looks old and frayed, replace it immediately before it leaves you stranded.

25 mpg is very good for an automatic. If you have a stick, you will get up to around 29 on the highway after you get a good oxygen sensor and any other problems cleaned up. That thermostat might help a little because the fuel injection system will now read proper engine temperature.

If you are doing the timing belt, you definitely want to replace the front seals on the crank, intermediate shaft, and cam. If it is the rear main seal leaking, wait to see if cleaning the flame trap helps, and even if it doesn't, park on a drip pan until you need to pull the transmission for some other reason. The rear main seal is a labor-intensive repair to undertake just to get rid of a drip.

Check the thermostat on the flapper door in the bottom of the air filter box. Make sure it closes off the preheated air when warm. If it fails, it will cook your mass airflow sensor ($$). After buying a new MAF sensor, some folks defeat the thermostat and seal the flapper shut to make sure it never happens again.

Take a good look at all your rear suspension bushings, especially if you have a stick and/or the car feels a little 'loose' or has a clunk when starting out.

If your defroster stops working on uphill grades (and it will), remove the check valve from the thin vacuum hose that attaches to the top of the intake manifold. Wash it in hot dish water, and it will be good for another decade.

That's all the tips I can think of for now.