GURPS Traveller Classic? Starting Point 4th Edition?

[Nedorus]

Having just finished a long-running fantasy campaign I'm looking for a new setting for my players to enjoy. Was looking at a space-oriented SiFi setting. Stars Without Numbers sounds like there is lots and lots of opportunity for adventure, so does Traveller. The latter having the BIG advantage of a GURPS version being available.

Before I dive into it too deeply I have some questions.

1. The GURPS Traveller Classic is 3rd Edition GURPS. How much does that matter? How easy is it to convert stuff and how much stats are actually in there?
   What about the other sourcebooks? How much "stat-conversion" would be necessary for them?
   
2. I'm looking at GURPS Traveller: Interstellar Wars, which is GURPS 4th Edition. Is this the recommended starting point for a first-time Traveller GM playing 4th ed? Would you recommend getting the 'Classic' as well?
   
3. I found GURPS Traveller: Psionics Institutes (also 4th Edition) and would be greatly interested in including Psionics from the start. Would you recommend to use this or rather rely on Psionic Powers for a starter? Are these two compatible?
   
4. Do you have any other recommended books/reads (incl. but not limited to novels) to get thematically deeper into the Traveller universe?

P.S.: I'm aware of the GURPS Update 4e document and have used it in the past to update some of my old 3rd edition stuff (mostly GURPS Classic: Bestiary). But it can still be a bit daunting when facing an entire sourcebook