So I can pick up a running 1.8 with about 45k on it, and was wondering what problem areas I should look for?

 

good compression and oil leaks, otherwise you should be fine. Maybe give the engine a once over 3 or 4 times after the install to make sure all hoses and whatnot are installed and clamped correctly. Also are you replacing the motor as a direct swap, or as an upgrade. Engines were: 89-93=1.6, 94-2005 1.8. Head design and compression ratio was changed in 1999?

Also, I think its a very very good idea before you get the motor going the first time, flush the oil. To do this, get the cheapest oil (and filter) you can and pour a quart or two straight through to get any crud out, then fill it with the cheapo oil and start it for 10 - 15 minutes until its good and warm and drain it as warm as you can stand. Now, get the good filter and oil on the engine and enjoy yourself.

 

I'd pull the front exhaust cam cap and check for wear on the top of the cap. That's a good indicator of oil/filter changes since it's last in line to get oil- and the trash usually winds up there.