lord of the rings - Did Frodo meet any of Valar or Maiar when he sailed to Valinor?

Yes, of course he could have.

However, there is no indication of whether or not he did or, if he did, who he would have met. Tolkien never wrote about the details of Frodo's (and Bilbo's) time in the Undying Lands, except to say that they eventually died there.

From his letters, Tolkien seemed to regard merely being in the Undying Lands as being a form of healing; from Letter 154, for example:

[I]n this story it is supposed that there may be certain rare exceptions or accommodations (legitimately supposed? there always seem to be exceptions); and so certain 'mortals', who have played some great part in Elvish affairs, may pass with the Elves to Elvenhome. Thus Frodo (by the express gift of Arwen) and Bilbo, and eventually Sam (as adumbrated by Frodo); and as a unique exception Gimli the Dwarf, as friend of Legolas and 'servant' of Galadriel.

I have said nothing about it in this book, but the mythical idea underlying is that for mortals, since their 'kind' cannot be changed for ever, this is strictly only a temporary reward: a healing and redress of suffering.

^{The Letters of J.R.R. Tolkien 154: To Naomi Mitchison. September 1954}

There may be some theology behind this that's beyond my knowledge, but there doesn't appear to be any specific expectation that Frodo would need "tending to."