Queries from a Cyper-newbie?

[Chris Avery]

Anybody willing to offer a bit of help to a cypher-newbie?  I'm trying to sort out a few of the basics:

(and if not answers, just a few pointers on where to go for info? ) Thnks.

1. PGP 5.0 -- good software? If not, what problems?  Why to use DSS vs/ RSA keys?  How is 5.0 different than 2.6.3i ?  Which is better?

2. Are emails encrypted using PGP 5.0 decypherable by PGP 2.6.3i (and vice versa?)  Using RSA keys? 

3. I understand certain encryption s/w cannot be legally exported, I am aware that such s/w is nevertheless being used (and built) abroad.  My queries:  Is purely domestic use being threatened by the pending legislation?  Is it already illegal to send an encrypted msg out of the US? If so, is it illegal to receive an encrypted msg from outside the US?

4. How strong is strong?  My MS Explorer has the 128 bit encryption scheme to secure domestic financial transactions (such as credit cards). How "un-encryptable" is this? I read some recent postings here re difficulty of breaking 128 bit keys -- but this had reference to stronger methods of encryption than MS Explorer uses, right? So 128 bits is hard to break (umptyump years, terrawatts, etc.)? Then why does my PGP 5.0 software offer keys that are 768, 1024, etc. up to 4096 bits in length? Are these numbers on the same scale? 

Any "strength" differences between RSA, DSS, and Diffie-Hellman? IS there some layman-understandable difference between these? 

5. Is international data traffic somehow monitored (or monitorable) to detect encrypted traffic?

Thanks for any help.