I recently had my dipstick guide snap on me and oil has gone everywhere. Will I be ok to wack some degreaser and then use my steam cleaner on it. If so should I cover anything up?

Cling film over electrics is always a good idea when cleaning engine bays.

A good degreaser/APC left to dwell and agitated then rinsed would make a good start.

Not used steam on an engine bay so can't comment on that, if it is necessary is up to you after you have given it a good clean with APC before hand.

Tesco doing Flash APC for just over a pound a bottle at the mo. 

Often this is found even cheaper and is a staple for many detailers

 

If you leave the engine running when you steam clean or snow foam as well as covering the electrics, ( if petrol)  my daughters Ford Ka