Check there is oil and coolant in it before you do anything else. It would be worth charging the battery so you know that's good too. You may find that the brakes have bound on, especially if it's been parked with the handbrake on. I would personally budget to replace at least the brake linings and tyres to give peace of mind. I'd also strongly suggest doing the cambelt because if it's been sat in one position for several years it may be on the brink of failure. Also well worth giving it a full service (oil, filter, fluids, spark plugs, etc...)
You may find that fresh petrol and a fully charged battery are all that's required to get it running but before you take it out on the roads you would want to replace quite a few service items. You can decide if it's worth spending the money after trying to start it.
With regards to the "slime", hot water, dish soap, a sponge and some elbow grease should quickly get rid of that.