you got a good deal. now relax and just get mixing, you'll realise that a tonearm upgrade is amongst the absolute last things you need.
invest some money in a spirit target level and stylus alignment guage, should only cost a few pennies and will help you get your decks setup.
isopropyl alcohol and a nice lint free no static cloth is a great way to clean your records. there are so many different methods of cleaning that get debated ad nauseum around the net. in 10 years of use over thousands of records and more hours behind the decks then i care to remember, isopropyl alcohol and a good cloth has worked flawlessly for me.
the rega/ol arms have proper geometry in terms of length and headshell angle. its just the stanton/vestax/etc etc straight arms are junk that attempt to solve a problem with the marketing department rather then with good engineering.
ellipticals sound better but track poorer, mainly on the back cue. they wear less, but again thats relying on correct setup.
service and calibration can be done at a regular technics/panasonic service centre but what i'd do is ask the guys at your local record store where they take their decks. i guarantee theyve all had to get them worked on at some point and there are a lot of techs like us who go out of our way to setup the gear properly and ensure maximum dj operability rather then just putting it in spec. at the same time you should get the cables replaced (its a matter of time before they fail) and get the ground wire removed, a good tech will do it for you.
a keyboard stand will work nicely with your case, just make sure your surface ends up being level
