Members of both sides of the conflicts were granted pardons. The Good Friday Agreement, which is basically the peace document putting an end to the majority of hostilities (at least, organized hostilities) signed in 1998, laid out the future political framework in a peaceful Northern Ireland. Both sides of the conflict, Republican (IRA) and Loyalist (UVF) made concessions to allow the deal to work. A large part of this was releasing prisoners.

To maintain the ceasefire, both Irish and UK Governments agreed to release prisoners jailed for crimes relating to the conflict, but there were conditions attached:

‘the prisoner is serving a sentence of imprisonment in Northern Ireland;

‘the sentence is one of imprisonment for life or for a term of at least five years;

the offence was committed before 10th April 1998 if the sentence was passed in Northern Ireland, the offence: was a scheduled offence; and

was not the subject of a certificate of the Attorney General that it was not to be treated as scheduled offence

if the sentence was [assed in Great Britain, the offence;

was committed in connection with terrorism and with the affairs of Northern Ireland; and

is certified as one that would have been scheduled, had it been committed in Northern Ireland

the prisoner is not a support of a specified organisation’ (i.e. each individual must be a member of a party involved in the ceasefire);

‘if the prisoner was released immediately, he would not: be likely to become a supporter of a specified organisation, or be likely to become involved in acts of terrorism connected with the affairs of Northern Ireland;

So basically, if you were an IRA member who met these conditions, you were eventually released from prison. It wasn't an immediate thing, prisoners were released over time following the signing of the agreement (1998) till June 2000. As to the issue of reintegration into society, this was a pretty serious issue that was considered. A lot of the pardoned prisoners were "run of the mill" low level guys, who decided to become freedom fighters in their teenage years. However, there was a small percentage of them who had committed massive atrocities such as the killing of civilians. This was a massive point of contention, particularly for the Unionist public of Northern Ireland, who had been subject to a large campaign of often indiscriminate violence by the IRA. These pardons were seen as rewarding men of violence.

Some legislators argued that the families of victims should be allowed veto the release of a prisoner, but this never made it into the agreement.

The Governments planned for reintegration by promising that:

In response a mechanism was inserted into the process to ensure that victims would be informed when prisoners responsible for or related to their loss were released, to allow time for them to emotionally prepare themselves.

The government of Northern Ireland was obliged to support released prisoners with employment opportunities, retraining and further education if requested through the Northern Ireland Association for the Care and Resettlement of Offenders

The European Union Peace and Reconciliation Fund invested £1.25 million to support prisoner re-integration schemes- distributed by the Northern Ireland Voluntary Trust- which assisted in financing a ‘self help model for reintegration’ managed by former prisoners e.g. the Republican organisation Coiste na n-Iarchimi. 27

‘If released, a qualifying prisoner must not be likely to become a supporter of an organisation not involved in the ceasefire or become concerned in the commission, preparation or instigation of acts of terrorism connected with the affairs in Northern Ireland.’

Edit to add: I entirely forgot to address the last part of your question, as to what happened to the pardoned IRA members after release. While it's obviously impossible to say what happened to all of them, or make blanket statements - The large majority of these people simply went back to living their lives as best they could. The "war" for the most part, was over. They had no conflict left to partake in. Moreover, you have to remember that many of these men (and women) had spent a large portion (if not the greater part) of their lives in incredibly oppressive jail conditions. Many would just have been happy to leave everything behind and enjoy what they had left.

Sources: Kieran McEvoy, ‘Prisoners, the Agreement, and the Political Character of the Northern Ireland Conflict’, Fordham International Law Journal (1998)