PS3 read disc problem. Need guidance

I recently bought a ps3 slim (Model NO. CECH 2001A). I was ecstatic to play my new game, specifically Metal Gear Solid Legacy Collection, only then to find out it doesn’t read the disc. It stays loading and about half way trough the disc makes an eject sound but the disc doesn’t come out and then a few seconds later it stops loading. These are the steps I’ve done so far:

Step 1: Downloaded the latest firmware, thinking that might be the issue.
Step 2: Factory Reset the console, suggestion of youtube searching.
Step 3: I’ve decided to go the website that TronixFix suggest, IFIXIT (very grate website, helped out a lot) Did step by step the troubleshoot options. I popped in a Blu-ray movie and it did not worked but the DVD movie did and just to make sure I also got a ps1 game and it played it well.
Step 4: the website suggest for the next step is to clean the lens. Despite my nervousness, opening up a console for the first time I did it. Cleaned it down with a q-tip and alcohol. Sadly this did not work.
Step 5: Final step from the website suggest its a faulty lens. ifixit doesn’t sell the lens itself but it does sell the optical drive (out of stock). I’ve been researching and found out that you have to make sure a serial number must match with the motherboard of the ps3 that the two are married and you cant just change with just any optical drive. The thing that is confusing me is in the ifixit website it just ask for your ps3 model number and there is the optical drive is there for sale (out of stock) and not asking anything else like MB serial No. or optical, blah blah.

My questions are:

  1. Is this true? I must open up the console and search for those serial numbers.

  2. Should I look for the whole optical drive? (according with ifixit it says its this model KEM-450AAA) or search for the laser replacement only?

  3. Does the laser suffer the same fate of “marriage”? meaning I have to make sure as well that they match.

  4. Any suggestions on where to buy the parts? Since ifixit has these parts out of stock, I’m assuming they are not going to get a resupply because its and old console. Looks like I’m searching at ebay and Amazon.

Any help is greatly appreciated.