I have just upgraded my Laney IRT112 cabinet which had a HH 1280 in it. Tools you need are number 8 spanner and a philips screw driver and gentle fingers.
Most upgrades are simple. I took the back off which was 10 screws and then carefully rested the back on the cabinet as the wire has two slide in connections to the speaker which you ease of carefully. They are not solded to the speaker they are N shaped connectors. Once I had done that I could move the wire and the back away. The existing speaker is held in place by 4 nuts on through bolts from the front. They came off easily and then you can lift off the speaker carefully. As long as you upgrading the speaker with the exact same size, in my case 12 inch Celestion G12H 70th Anniversary. When the speaker comes you have to attach the foam strips which are cut out to go on the edge of the cone of the speaker. They are self sticking just peel back the self adhesive sticky. Once you have dont that you carefully lower the speaker onto the 4 bolts with the two connectors at the top and in the same position as the speaker you removed. You then put the washers and nuts on one by one carefully and tighten carefully, not too tight but so you havent squished the foam. Now get the back slide the connectors in as they were on the previous speaker that is red on the left and black on the right and make sure wire isnt flapping too much by attaching either to the speaker with tape or to side of the cabinet. Then carefully affix the back initially with 4 screws. Then go test the speaker and if it is all ok and working then put the other six screws in, job done.
The whole thing took 15min to take the speaker out, 5 min to prepare the new speaker, 10 min to put the speaker in and about 5 min to test and finish off the remaining screws.
Last time, I paid to have this done and waited a week to get in the queue for other jobs. Cost me about £20 in Thailand which is not much, but now I thought I would do it myself.
So Be Confident its easy to do!