My opinion.. you should no loose any configuraiton that is currently running on 7.2, I upgraded to this version from 7.2 for the need of eigrp support and did not loose ssh access from the inside interface nor I lost RA vpn configuration, I would not suspect l2l configuration would be lost but cannot speak for this portion as I did not have at the time l2l configs , my upgrade was conducted local where I could reach the firewall in the event of failures.
How remote is remote? In any case, I would suggest that you go over the upgrade notes if you happen to be upgrading to the latest version 803, cisco is very good at noting risks , look at the caveats resolved and unresolved , the cli syntax remains other than new commands added based on the new added features on version 803 that 7.2 does not have.
http://www.cisco.com/en/US/products/ps6120/prod_release_notes_list.html
Jorge Rodriguez