SR20 Clutch Blew or Something Else??

[Hayashi]

K first off i bought the car with the motor in just not finished...so me and my friend did the wiring and all that stuff and we got the car running, come to find out that the first few times we started the car there was no oil in the tranny. So we put some inside, but when you drive the car in low rpms when down shifting it made a wierd grinding noise. and tonight when i was driving it I felt the clutch slipping well i think it was but when i got to a certain point i heard a pop noise and the car shut off. while rolling I started it back up and it would just rev..(why i think the clutch went..) but when i came to a stop and turned it off the car wont start it makes a wierd noise. Flywheel gone and clutch blown?
One more quick question...billet steel flywheels any good or what about Chromoly Lightened Flywheels? i did a search and all i came up with was aluminum =)