I'm not a druid and haven't played my druid beyond 13 so take my advice with the pinch of salt it undoubtedly deserves...
I'll agree with what the above posters have said regarding when to respec.
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I don't have *any* healing gear right now - would have to buy it all.
Any gear, healing or otherwise, you buy in the levels between now and outlands is going to be pretty much superseded so don't worry about it, you'll pick up gear from quest rewards and instances there. When you are in outlands if there isn't a reward that suits your current spec then simply pick one which you can use when you do respec.
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Less solo viability (is this true?)
If a holy priest *waves* can solo outlands then so can you, might not be quite as quick as you're used to but you still have your forms to help even if you don't have the added talent bonuses associated with DPS or whatever.
I'd not think you need loads of practise healing right now, you can wait til the early outlands for that (ramparts and BF) if you respec later then just keep trying til you get comfortable with a good healing style. I did things the hard way on my priest, namely the levelling as holy, simply because I wanted the experience healing... it really wasn't necessary, up until outlands all the instances were fairly easy to handle and yes I guess it may become second nature sooner the earlier you do it but you're only going to be missing a week or so practise so no big deal :)
Just throwing my opinion into the mix as I was passing through on the way to the kitchen for a hot chocolate :p