Your existing drive could be showing signs of age. I think you can get a cleaner for the actual lens. Are you sure the problems aren't associated with region encoding? Has it always taken time to install your programs or has it only just started and the DVD drive appears to be struggling to read the discs?
Your DVD-ROM drive is probably 6x. The only DVD-ROM speeds I've actually heard of are 1x, 6x, 12x and 16x, but if yours is 5x I'm not going to argue with that.
With a 12x or 16x DVD-ROM drive, the speed for reading CDs and DVD-ROMs will obviously be faster. You won't notice any difference if you are using the drive to watch DVD movies. I have a 12x Artec (3 or 4 years old) and a 16x LG (12 months old) and I must admit that the Artec one seems a bit better build quality - the tray comes out very smoothly and it is fairly quiet. The LG is a good drive, but the tray sounds a bit rougher and is quite loud. However, I've seen other LG drives of a different design (more rounded off buttons, etc) that are quieter opening and closing the tray, but the same reading.