Replacing engine with bigger one surely make the car faster but it has certain issues. The swap is not like change of brake pads or change of tyres, it in fact it is a complete change in engineering design of car which can cause several adverse effects resulted in much frequent trips to mechanic and much more maintenance cost. Shocks and suspension will also be effected due to increased load and even repairs/replacements will not bring your car to its original form.
The resale will go down drastically as well. If your engine is weak, I would recommend selling the car and buying something with better engine. If the body is in really bad shape and resale is already low than go for engine swap and best of luck.