If I knew someone were willing to do it for $20 (or GBP) I would let them. I'm fairly handy with a precision screwdriver and a beer, but I have watched the videos and after my friend telling me he has done 4 (without) issue and found it hard, I worry about myself. That said, it is something that requires you to basically tear the entire computer apart, it is not a user upgradeable item according to Dell and could void your warranty. If a shop will do it then I'd let them.
Having had my mini for about 3 days now running SL I must say that extra gig would do wonders.