1992 Toyota Celica GT Oil Leak Question

1992 Toyota Celica GT Convertible
2.2 5SFE 201,000 miles on car and 80,000 miles on used engine
5 speed manual transmission

I just discoved a new problem with my Celica. I just got a tag on it this past Monday and have been able to drive it. It does have a bad oil leak but not severe. I haven't had a chance to fix it as I had to leave it at the trim shop to get the top reconditioned. I suspect it's coming from the oil pump. The engine was replaced with one from a local junk yard with 80,000 miles on it. I do not know how long this engine sat before being installed in my car. I drove the car to my moms house probably 10 miles away and on the trip back (about 18 miles into the round trip) the oil light started to flicker. It seemed to flicker more as I accelerated. I went home and checked the oil. It was to the full mark. The oil was just changed and has less than 30 miles since changed. I went ahead and changed the oil filter and the oil pressure sending unit since it was cheap. I drove the car about 5 miles and it started flashing again but much sooner than the first time it did it. I'm using 10w 30 oil. I can turn the car off and wait just a minute or two or just 30 seconds and start it back and the light is not coming on but after a couple minutes of driving it will return and slowly begin to flicker until it stays solid with random flickering. Any thoughts or opinions or personal experiences are greatly appreciated. I really hope to be able to fix this problem as I just paid 1500 for it AS IS and another 200 to get the top resewn.

Updated...

I just took the valve cover off and what I saw scares me. There is crusty burnt up oil all over the place. It's around the spark plug tubes and the side of the head toward the front of the car. The stuff is very ash like but oily. It's like burnt sludge I guess. If this stuff got washed down to the oil pan it would have to be blocking the oil pumps pickup tube screen for sure.
Take a look and tell me what you think...
http://i329.photobucket.com/albums/l375/doug2060/100_1912.jpg
http://i329.photobucket.com/albums/l375/doug2060/100_1914.jpg

More photo's below... I got the oil pan and pickup tube off. I cleaned the screen off just a bit with carb cleaner. It didn't appear to be overly clogged up but was covered with this debris. The pan was thick with the stuff to the point that it dumped out in clumps. I should have took a photo of it before but you can clearly see this crap all over the inside of the pan. There is no way in hell this is an 80,000 mile engine... Can 80,000 miles really look like this?

I can tell someone has been in here before. The oil pump has clearly been replaced at some point and the pickup tube had rtv silicone instead of a proper gasket. It was probably losing pressure at where the pickup tube bolts to the oil pump as the rtv appeared to be pushed out and hanging. I will make a new gasket from a sheet of oil resistant rubber fiber and clean this crap up as best I can. I can't be 100% sure this is my problem but it damn sure looks that way. Any and all thoughts and opinions are welcome here.

http://i329.photobucket.com/albums/l375/doug2060/100_1916.jpg

http://i329.photobucket.com/albums/l375/doug2060/100_1920.jpg

Cleaned out oil pan and pickup tube...
I have notified the junk yard of the problem and they have agreed to extend the warranty to 90 days. I let the car sit overnight so the RTV sealing the oil pan could set up. I filled it back up with 10W-30 and drove the car several miles without so much as a blink of the oil light. I plan on changing the oil again VERY soon and each time I do it over the next few months I plan to drop the pan and pickup tube for cleaning.
While I was at the junk yard they showed me a similar engine from a Camry with 120K. They took the valve cover off and it was far worse than mine was. The guy tried to tell me they are all like that... BS... The bad thing about it was they are actually planning on selling that motor to someone knowing about all that crap in it. I think I'll be buying my used parts elsewhere in the future. Oh yeah, He also let me know my engine had been sitting on the shelf since before they got their computer system in 2002 so there is no telling how long it actually sat around. I guess I can look forward to changing all the seals very soon too but I kinda expected that anyways.
I know I didn't receive a whole lot of help on the several forums I have visited but it's good to take a break and vent frustration through a keyboard. It really gives you time to think and come up with options. Hopefully my posts can help others throughout the interweb with shit filled Toyota engines... LOL...