Also going on the 19th to the Iglika - part of the crowd with the matching red hats (see the "My Mum In Boro... post!). Look out for us Richard !
Went same week last year. For clothing just take loads of different layers then you can / remove as you need. As a beginner you will probably spend the first morning on the slopes by the Rila so easy to pop back to your room at lunch if you've got it completely wrong clothing-wise.