I wonder how much it's changed in those 14 years since I went? I just googled the temples (which was a nice trip down memory lane) and it does seem to be a lot more popular than when I went. I think i was very lucky to go when I did as a couple of "lesser" temples I visited I had all to myself! There's a central area of temples which you can go to and walk around without transportation (and I guess will be very busy) but there are many others that require a drive out to. I suppose there will be tours you can buy both individually or as a group from Siem Reap. And if you arrive there independently people willing to sell you their services as a guide - with varying levels of quality. Otherwise you can just rock up and walk around at your own pace. You could do the central bit for a few hours and then head out to one or two of the more distant temples. Up to you I guess what sort of experience you want. I hope it's worthwhile.