The link below explains the difference between CAV and CLV Laserdiscs. I prefer The Definitive Collection (DC) LD's which are CAV.
CAV vs CLV
The DC set uses the same masters as the THX Faces CLV LD's which came out sometime later. The only problem is that the Definitive Collection had the problem of the missing Leia footage in the first pressing. I got lucky when I got mine. If you go after the DC set, make sure to ask the person if the footage is there or not. Also, the DC has all of the extras. Now, I have a friend who is using both sets to do their conversion because the DC set is a little tough to IVTC properly because of the pattern getting thrown off during the side breaks. Check the link for more information on IVTC. Also, do a search for Star Wars Conversion on the site and you will see a huge thread at here that discusses how others are doing the conversions.
As far as the C-3PO and the "Close the blastdoors!" lines, I would use the Special Edition LD's for those if you have access to them. It may be a little pain, but you could extract the audio for those two lines from the SE LD's and insert them into your Original Version conversions.
As far as Laserdisc Players go, I would go for one from Pioneer. I have the CLD-D703 which I consider to be second best non Elite LD Player they made. The D704 is exactly the same as the D703, but it features AC-3. However, the D703 can be modified. One of the best LD Players to get is the Elite '97 in my opinion. There is actually a huge argument between Elite '97 and Elite '99 owners over which is the best player. I don't remember where it is at, but someone also had a link to a gold colored LD Player that was something like $5000. That is too much for me though. The Elites are pretty expensive as it is. This link has a large amount of information on various Laserdisc Players divided up by brand.
I have done one conversion myself which I was happy with until I saw how much better others could do. I used the S-Video out of my LD Player and connected it to my ADVC-100 DV Capture device. I noticed there was a lot of dot crawl in the reds and other bright colors. Since LD is a composite format and my player has inferior Y/C separation compared to my capture device, I'm going to use composite instead of S-Video. I may even invest in a WinFast TV2000 Expert card because I believe it can capture in the 4:2:2 colorspace instead of the 4:1:1 colorspace that my ADVC-100 is limited to.
Anyway, I hope this information helps.
Patrick