We've been cooking on Aga's and Rayburns for about 30yrs i guess now, used oil, gas and now wood. A few comments:
Make sure you have a 2nd cooker, gas or electric (ie a regular oven and hot plate) Aga's and Rayburns are "always on" so in summer you will need an alternative method of cooking
Defiantly get some decent books, Carol Bowen is excellent as are Mary Berry's old books (nearer ones are slightly naff)
DEFINATELY (I mean 100% do) get decent long oven gloves, Aga type go up your forearm, if you don't you'll have brand marks on your inside wrists...
You need to think ahead, remember an Aga or Rayburn can take 1-2hrs to get to hotter temperatures os say +180, even more for roasting at +200º
Use Astonish it's the best cleaner of enamel surfaces and will last years
Yes it will drink oil, perhaps £200-300 a month ? they are super inefficient in that respect (Rayburns are typically better than Aga's in that)
Although we've had gas, oil and wood we wouldn't want to run anything other than wood now, the cheapest fuel but also the trickiest to manage
Baking is just a pleasure and you'll learn to really enjoy it, you'll hopefully get the bug !
Keep your leccy kettle for summer, you'll need it unless you want to melt in your kitchen
If you do want to re-enamel the Aga i'm sure you can get it done for much less, i bought a completely refurbished Rayburn for less than that only 5yrs ago, dragged it across Europe in the back of a Landy and it now sits in our kitchen, it's run from about Nov - March/April.
Good luck and enjoy it (certainly would take it out

)