Welcome to the site!
You have a lot of questions (good!) -- I'll try to hit them all:
- It is possible to change to a 3, 5, or 9 line game, although the reel strips for the multi-line games are typically different from the single-line games, so you'd likely need new reel strips, along with new reel glass, award glass, and EPROM chips. The following FAQ provides detailed information on what's needed to change from one game to another:
http://www.newlifegames.net/spset/gamechange.htm- An easier option would be to change your game from a 2 Coin Multiplier (2CM) to a 3 Coin Multiplier (3CM). You would need a different award glass to show the 3-coin payouts, and a new SS chip. Your reel strips likely can remain the same. The IGT Bible on the site shows the different payback chips available for many S+ games -- click on 2CM or 3CM at the top to see the different chips available for your Triple Diamond game.
http://newlifegames.net/igtbible/- If you're inserting quarters and they're getting "eaten" without giving credit or causing a tilt, you likely have a large coin encoder in your coin-in optics. If you can post a picture of the coin-in area (the inside of the machine, with the door open) that would be helpful.
- The bill validator in your machine is a garbage Western Money Systems validator retrofit. They're not worth trying to fix, typically, but someone more familiar with them would have to tell you what part(s) you're missing. Additional photos would be helpful. Generally speaking, though, it's probably a lost cause.
- You conceivably could change out the reel glass and install a different LED display bar to move the credit displays below the reels, but it would likely be more trouble than it's worth just to move them there for the sake of moving them.
- You will not be able to convert this S+ machine to a Wheel of Fortune machine. Even a newer S2000 machine would be very difficult to find all of the parts needed to convert to a Wheel of Fortune machine -- it's taken some people years and years to put theirs together.
- There are a couple of "Spin 'Til You Win"-type game kits out there for the S+, which would require changing the glass, reel strips, and chips to a new kit. Spin 'Til You Win, Coral Reef, and 4th Of July offer that feature, off the top of my head. Those kits are difficult to find, though, as they're sought after due to their unique features.
- You could add a Mikohn ChamII+ progressive controller and meter to your S+ machine. Look in the Mikohn Progressive section of the site for more information on those.
- Another option would be to add an IGT "mini photon" progressive. Check the IGT Stand-alone Progressive Systems section of the site for more info.
Good luck with your new machine. Be careful -- they tend to multiply and fill up your house!