ahh,
Sorry I wasn't clear there. I should written $300 "oil change." Yes, you are correct, there are other things that are to be checked during any service. However, I have watched two techs do a scheduled "service" and both did only an oil change at that service. They certainly didn't lift the mats, clean and dry the floor as suggested in the manual. One lifted the car, took off the oil plug, went out for a smoke while the oil drained, put the plug back in, lowered the car, put in "about 5 quarts" of oil, drove the car off the lift, filled out a ticket and went on the the next car. That was a $300 oil change. (BTW if you don't have the manual you really need to download at least the service schedule from andy's link above -- it is the same for the later years as well).
I have done my own service, except for the 1000 mile service, with the blessing of my Lotus Service Manager. At his request, I have every receipt for items purchased and have documented dates, mileage, etc. for each of the services. I also follow a tighter service schedule (oil changed more frequently, etc.) than Lotus' recommends, but that's just my choice.
This is all, of course, just my opinion. If you are not comfortable with working on your car, obviously get someone else to do it or, again just IMHO, have someone teach you how. As andy has said, keep records and your warranty will be fine.