Cosmo,
I asked you how to proceed to an RNAV point raw data, not by proceeding VFR or Dead reckoning.
Providing you have a VOR/DME in range, you can use the
fix-to-fix navigation technique. It takes a quite a bit of practice and mental gymnastics but for two crew should be doable. I'll conceed that it maybe a bit but unrealistic in modern airspace given that when vectors are unavailable, so are navaids!
As for IRS drift, the 737 Clasic is meant to be RNP 12 without updating. In my experience I wouldn't bank on it though!
And another exclamation mark for good measure!