Not a solicitor or expert on capital acquisitions tax, however I see it as follows:
1) On the original division of the assets by the solicitor, assuming the will said that each of you were to get 1/6th share of the house and 1/6th share of the land, then the solicitor should have suggested that you all could have availed of an option to "disclaim in consideration". Assuming house worth 600k, and land worth 300k, Effectively you would end up giving your 50k share in the land for receiving an equivalent 50k share in the house, but the disclaimer in consideration could have been extended to adjust for the monetary value. This would then have left you in the position of having full ownership of the house plus a cash adjustment owing to your other siblings of say €450k using the above example),. Unfortunately its too late to effect a disclaimer for consideration once the will in finalised. However this was an obvious point which your solicitor should have discussed with you.
2) The disposal now of your share in the land, and your siblings share in the house is a disposal for Capital Gains Tax purposes (and possibly capital acquisitions tax if the values do not match). If the will was only administered a few years ago, then perhaps the land values and house prices may be favourable in doing the swap - i.e. there may be no "gain". Also you will need to consider stamp duty.
Kieran Coughlan, Tax Manager, CXC